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Forcep Deliveries
COMPLICATED LABOR AND DELIVERY I
0095-5108/95 $0.00 + .20
DELIVERIES James P. Thompson, MD
The increased incidence of cesarean sections and the tendency to manage labor more actively in recent years has caused many to reevaluate the role of forceps deliveries in the modern day practice of obstetrics. On the one hand, cesarean sections done early in labor negate the consideration of forcep use. On the other hand, higher-dose oxytocin stimulation is continued often until spontaneous delivery of the vertex occurs. Coupled with these trends in labor management is the realization that for the past two decades there has been an apparent reduction in the importance of forceps deliveries in many of the obstetric residency training programs. In some programs, the use of forceps is barred entirely, thus, depriving residents of gaining an awareness of both the potential benefits and risks of a previously thought useful obstetric practice. Efforts to curtail the rising cesarean section rate include more liberal use of oxytocin, more concentrated nursing attention during labor, and a reaffirmation of vaginal operative skills. It is appropriate, therefore, to review the principles that have guided our use of forceps in the past.
HISTORICAL REVIEW
The use of forceps dates back to ancient times. One thousand years before the birth of Christ, Hindu writers described a knife and hook that were used in difficult labors to destroy the fetal head and extract the
From the Department of Obstetrics and Gynecology, University of Medicine and Dentistry of New Jersey, Newark, New Jersey
CLINICS IN PERINATOLOGY VOLUME 22 • NUMBER 4 • DECEMBER 1995
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fetus. In 400 BC, Hippocrates wrote of delivery by traction. Avicenna, a Persian physician who lived from 980 to 1037 AD, demonstrated their use and Albucasis prepared an illustrated series on forceps, including an instrument with teeth on their inner surface to obtain a better hold on the fetal head. The word forceps is derived from the Latin formus meaning instrument and capio meaning to seize according to Dill. 3 The concept of forceps as we know them today dates back to the late 16th century when Peter Chamberlen introduced the first instrument to be used for the delivery of a living infant. Prior use of the forceps was limited mostly to destructive procedures followed by extraction. Chamberlen's design was remarkably simple and it included a pair of fenestrated blades approximately 12 in long that crossed outside of the vagina. The blades were designed with a cephalic curve to better grasp the fetal head. Contributing to the lore of obstetrics, it is said that succeeding generations of the Chamberlen family kept the design of this instrument a closely guarded secret for over a century. In 1745, Smellie advocated application to the fetal head with the posterior fontanelle as the point of reference rather than the previously practiced pelvic application. Soon after, Levret introduced an instrument with a pelvic curve that included also a wing nut type of articulation, later referred to as the French lock. In the United States, the first historical account of the use of forceps was that of James of Philadelphia in 1812. Simpson developed an instrument with a long cephalic curve to the blades and an interlocking handle in 1848. A decade later, Elliott devised a forcep that was smaller and lighter and had a rounded cephalic curve that was thought to be better adapted to unmolded heads. Both of these prototypes, virtually unchanged from their original designs over 100 years ago, are used on a daily basis in delivery units today. In 1877, Tarnier using principles of physics espoused by Pajot and descriptions of pelvic anatomy by Carus introduced the principle of axis traction. Significant changes in forcep design and versatility came about early in the 20th century. In 1915, Kielland introduced an instrument especially for rotating the head when arrested in the transverse or posterior position. The absence of a pelvic curve and the creation of a sliding lock on the handles for correction of the asynclitism that frequently accompanies transverse position of the head have made Kielland forceps especially useful for rotation. The first truly innovative contribution of an American to forcep design was that of Barton, who in 1925, designed an instrument to resolve transverse arrest and asynclitism that included a hinged anterior blade, sliding lock, and traction bar. During the same time, forceps designed to deliver the after coming head in a breech presentation were introduced by Piper. Increasing use of the prototypic instruments with fenestrated blades lead to the observation
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that compression of the vaginal wall between the openings lead to lacerations and, in 1937, Luikart modified the blades of the standard types of forceps by obliterating the fenestrated portion. He incorporated hollowed out indentures on the inner surfaces of the blades to facilitate grasping of the fetal head and decrease pressure marks on the face of the newborn. The surge of interest in the use of forceps occurred after De Lee's assertion in 1920 that the prophylactic use of forceps coupled with an episiotomy decreased trauma to maternal tissue and protected the fetal skull and brain. Although scientific data documenting the merits of his claim are lacking, the incidence of forceps use exceeded 50% in many institutions during the next 20 years. The introduction of antibiotics, safer use of blood transfusions and anesthetic agents, and the liberal use of cesarean sections have resulted in a marked decrease in the use of forceps currently. Innovative design, modification, and refinement have lead to the description of over 700 types of obstetric forceps. Save for the four or five basic instruments, the remainder are noteworthy only from the historical standpoint.
CLASSIFICATION
The increasing use of forceps brought about the need to describe accurately their mode of application. The level of the fetal head in the maternal pelvis and the location of the sagittal suture and posterior fontanelle of the fetal head at the time of application provide the basis for classification of forceps operations. In an attempt to standardize the nomenclature describing forceps use, the American College of Obstetricians and Gynecologists defined outlet, mid and high forceps in 1965. 1 The latitude between outlet and mid forceps created a good deal of confusion in that most applications did not meet the requirements of outlet forceps nor did they imply the necessary surgical skills or legal connotations of mid forceps; thus, the majority of forceps applications were classified as "low" although that definition was not included in the 1965 definition. In addition, the use of high forceps soon became unacceptable because of the high incidence of maternal and neonatal morbidity that often accompanied their use. In an attempt to clarify this disparity, the ACOG formulated a new definition that was introduced in 1989. 2 This is essentially a three level classification marked by the relationship between the leading bony portion of the fetal head (not caput formation) and the ischial spines of the maternal pelvis. The newer definition does not give special preference to the position of the posterior fontanelle; thus, delivery of the fetal head
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presenting as an occiput posterior from the + 2 station in the posterior position is considered now a low forceps, whereas it was previously a mid forceps operation. Comparison of the old and new definitions is shown in Table l. A recent survey of residency training programs revealed that 99% of program directors were familiar with the new definitions, but 20% of them did not use them when defining forceps operations. 10
PREREQUISITES
Prior to the application of forceps, there are certain conditions that must be met. Thorough knowledge of the anatomic characteristics of the maternal pelvis is determined best by a manual examination. Correct diagnosis of the position of the fetal head as marked by the locale of the posterior fontanelle should be made. This determination is often made
Table 1. AMERICAN COLLEGE OF OBSTETRICIANS AND GYNECOLOGISTS DEFINITIONS OF FORCEPS DELIVERIES
Classic definitions Outlet forceps Scalp visible at introitus without separating labia Skull has reached pelvic floor Sagittal suture is in anteroposterior diameter of pelvis Midforceps Head engaged Conditions of outlet forceps not met Artificial rotation High forceps Application of forceps before engagement of fetal vertex New definitions Outlet forceps Scalp visible at introitus without separating labia Skull has reached pelvic floor Sagittal suture is in anteroposterior diameter or right occipitoanterior, left occipitoanterior, occipitoposterior Fetal head at or on the perineum Rotation cannot exceed 45 degrees Low forceps Leading point of skull 2: + 2 Rotation s:: 45 degrees Rotation > 45 degrees Midforceps Head engaged Leading point of skull is above + 2 Adapted from American College of Obstetricians and Gynecologists. Operative vaginal delivery. ACOG Technical Bulletin No. 196. Washington, DC, American College of Obstetricians and Gynecologists, 1994, p 2; with permission.
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best in the later part of the first stage of labor prior to the occurrence of molding which often obscures the bony landmarks. Triangular in shape, the posterior fontanelle is formed by the union of the sagittal suture and the two lambdoidal sutures. The anterior fontanelle is formed by the union of the sagittal suture with the two coronal and the frontal sutures. Palpation and outlining of the posterior fontanelle is the desired method of determining the exact position, but in instances in which it is difficult, location of the anterior fontanelle coupled with palpation of the orbit or an ear will suffice. The fetal head must be engaged. Currently, this implies that the leading bony point of the fetal skull has reached the level of the ischial spines. If the face is presenting, the chin must be at the level of the spines. The cervix must be dilated and retracted completely. Often with oblique positions and direct occiput posteriors, the cervix will be dilated completely but not retracted completely. To prevent trauma to the cervix, it must be "gently retractable" prior to application of the forceps. Membranes must be ruptured. Catheterization of the bladder and manual compression of the posterior vaginal wall to empty the rectum will help decrease trauma to adjacent maternal organs. The patient should be positioned well down on the delivery table with the buttocks overhanging by at least 1 in so that proper axis traction can be maintained. Although not essential, an episiotomy helps decrease soft tissue resistance and limits the amount of traction necessary to deliver the fetal head. As with any surgical procedure, adequate anesthesia must be used to diminish maternal anxiety and pain. Pudendal block often will suffice for outlet forceps in the well-prepared patient. Low and mid forcep operations often require conduction anesthesia in the form of a saddle block or epidural. On rare occasions, inhalation anesthesia may be required and it is essential that an experienced anesthetist be present and that intubation be considered to prevent aspiration of gastric contents. Familiarity with the types of forceps available is essential. There is no universal forcep and the days of "learning one instrument and using it well" are over. Refinements in design have resulted in the construction of instruments with special features for dealing with variations in pelvic anatomy and positions of the fetal head. Electronic fetal monitoring techniques should be continued right up until delivery of the head. Placement of an internal scalp lead will permit this and aside from the minor annoyance of the electrode wire, will often prove reassuring and will decrease haste in extracting. Biochemical modes should be available also. Personnel experienced in neonatal resuscitation should be present in the delivery room for anything other than an outlet forcep delivery. A list of the prerequisites appears in Table 2.
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Table 2. PREREQUISITES FOR THE USE OF FORCEPS
Knowledge of pelvic anatomy Awareness of position of fetal head Cervix completely dilated Membranes ruptured Bladder, bowel empty
Familiarity with types of forceps Surgical environment Proper anesthesia Suitable monitoring techniques Facility for newborn resuscitation
INDICATIONS
Maternal indications for the use of forceps include the inability of the mother to exert adequate propulsive efforts owing to exhaustion or the presence of a conduction anesthetic. Prolongation of the second stage of labor is no longer limited to 2 hours if fetal heart rate monitoring techniques indicate no distress and progress in descent continues. Edema of the vagina and vulva will often be time-limiting factors but in their absence and with no signs of fetal distress, the second stage of labor may continue for a reasonable length of time beyond 2 hours. Medical complications of pregnancy that tax maternal reserve may provide indication for the use of forceps. Shortening of the second stage of labor is beneficial often to patients with heart disease, neurologic disease with increased intracranial pressure, and pregnancy-induced hypertension. Obstetric complications of pregnancy such as abruptio placentae may warrant early intervention. Fetal indications for the use of forceps include failure of further descent of the fetal head already well down in the pelvis, rotatory arrest, and selected malpresentations. The pliability of the fetal head leads to molding and when the head is at an advanced station in the pelvis and the decision is made that spontaneous delivery is unlikely in the next 30 minutes, forceps are best applied prior to the obliteration of bony landmarks and before the head is elongated to the degree that the toes of the forceps will not obtain the desired purchase point. Fetal heads that arrest in the oblique or transverse diameter are rotated best to the anterior position to facilitate spontaneous delivery or extraction. The persistence of an occiput posterior position often leads to deflexion of the head and creates the need for increased propulsive effort. Rotation to the occiput anterior position frequently leads to further descent and spontaneous delivery. Fetal distress, usually in the form of bradycardia, is often best handled by delivery with forceps rather than by allowing labor to continue or resorting to emergency cesarean section. It is mandatory that all of the prerequisites be met prior to the application of forceps for the latter indication.
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CONTRAINDICATIONS
Failure to meet the prerequisites for the use of forceps implies that another route of delivery be considered. The inability to evaluate adequately the maternal pelvis, such as may happen when confronted with a patient in labor and a history of previous trauma to the pelvis or the finding of an inadequate pelvis on manual examination, are contraindications. Doubts about the position of the fetal head or the presence of macrosomia should lead to exclusion of forceps as the route of delivery. The cervix should be dilated completely because the use of Duhrssens incisions is indicated rarely, if ever. Lack of familiarity with the various types of forceps and their potential for harm with improper use should also mitigate against their use. Controversy exists over the concepts and use of the terms "trial of forceps" and "failed forceps." Douglas and Kaltreider4 introduced the concept of trial of forceps and stressed the intent of the operator in carrying out the planned procedure. If an honest attempt is made to apply forceps to rotate or extract and resistance met with cessation of efforts before the occurrence of maternal or fetal injury, there is a place for trial of forceps. All too often, this designation is applied to vigorous attempts to deliver without success and a true failure of forcep delivery results. The semantic differentiation between the terms is often retrospective and confusing. Errors in judgment in applying the forceps and attempting delivery should not be confounded by the incurrence of maternal or fetal injury.
FORCEP DESIGN
Forceps are the primary surgical instrument of the obstetrician. As such, their use should be limited to the appropriate area-sterile environment, ample light source, and room to work-and governed by the operator's knowledge of the instrument. All forceps consist of blades, shanks, handles, and locks. The blades are the portion that is applied directly to the fetal head. Most are fenestrated. The pelvic curve of the forceps lies in the relationship of the blades to the shanks. To best appreciate the extent of the pelvic curve, the forceps are placed on a flat surface and the extent to which the tips of the blades rise above the horizontal plane defines the pelvic curve. This is designed to correspond to the curve of the maternal pelvis. The cephalic curve is defined by the rounded portion of the blades (Fig. 1). The Simpson's forcep has a long, tapered cephalic curve designed to use with molded heads, especially of the type found in primiparous patients. DeWeese and Tarniers' forceps are variants of the Simpson's forcep. The Elliott's forcep has a
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Figure 1. Illustration of DeWeese's forceps (left), Simpson's forceps (center), and Elliot's forceps (right).
Figure 2. The French lock is represented on the forcep to the left and the English lock is found on the forcep to the right.
Figure 3. Leffs forceps. Note the long, tapered, cephalic curve, and the bar at the end to facilitate rotation.
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shorter, rounded cephalic curve for use in multiparous patients who have not had a prolonged second stage and in whom molding of the fetal head would be unusual. Bayley-Williamson and Tucker-Mclane forceps are variants of the prototype with the latter also having a nonfenestrated blade that makes it particularly useful for rotation. The shanks of the forcep connect the blades to the handle. Most cross outside of the vagina after insertion of both blades, but Simpson's forceps remain separated right up to the point of union with the handles. Elliott's forceps have shanks that are crossed in their entirety. Parallel forceps such as those Shute designed have noncrossing shanks, and use is dependent on the maintenance of parallelism throughout the length of the forcep. The length of the shank determines the extent of the degree of traction that may be obtained. The longer the shank, the greater the traction. Handles are hollowed out usually and contain finger grips to assist with traction. Although they vary in length, a good general rule is to grasp the handles as close to their shanks as possible to decrease the amount of traction. Conversely, if more traction is required for delivery, a longhandled forcep grasped at the end will provide for more traction. Locks are located at the intersection of the shanks and are designed to prevent slippage following correct application. Terminology describing the types of locks is based on the country of origin (Fig. 2). The English lock, by far the most common, has a fixed notch on one blade to which the other blade is articulated following application. Simpson's and Elliott's forceps both have locks of this type. The French lock consists of an adjustable screw and wing nut located on one shank that fits into a groove on the other. Useful modifications of forceps include changes in each of the components designed to meet the clinical variations encountered. Leff forceps have a long cephalic curve, small pelvic curve, and a small bar at the end of the handle all designed to facilitate rotation (Fig. 3). Kielland's forceps have virtually no pelvic curve to the blades and a sliding lock that allows for correction of asynclitism prior to rotation. Barton's forceps have a hinged anterior blade that is flexible over an arc of 90 degrees and a traction bar. By exerting downward traction on the bar following application in the transverse position, the vector forces are resolved through the hinged blade so that rotation occurs when the vertex encounters resistance from the levator musculature. Piper's forceps are long and springy with their pelvic curve designed for flexion and extraction of the aftercoming head. FORCEP MANEUVERS
Proper application of the forceps must precede the two principal purposes for forcep use which are traction and rotation. Using the
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posterior fontanelle or occiput as the point of reference, the blades are applied to the lateral portions of the fetal head. If the occiput is directly anterior, the left blade of the forceps is grasped in the operator's left hand and applied to the left side of the maternal pelvis. The operator's right hand should be inserted into the vagina prior to the forcep blade, and the tips of the fingers should guide the toe of the blade into position while the thumb should rest on the heel of the blade (Fig. 4). An assistant should hold firmly the handle of the forcep in place while the operator inserts his left hand into the vagina and guides the right blade to the right side of the fetal head on the right side of the maternal pelvis. If the occiput is positioned obliquely, the posterior blade should be inserted first. In the case of left occiput anterior, application is identical to occiput anterior. If the occiput is to the right of the midline, the right blade should be inserted to the right side of the maternal pelvis to provide support while the left blade is inserted. The left blade is positioned higher on the fetal head and the handles must be crossed over
Figure 4. Finger tips are used to guide the toe of the blade into place. (From Dennen PC: Forceps Deliveries. Philadelphia, FA Davis, 1989; with permission.)
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one another to lock When the occiput is directly posterior, forceps application is identical to that of occiput anterior. Prior to insertion of the forceps, it helps to make a "phantom application" in which the forceps are aligned outside of the vagina to correspond with the position of the fetal head (Fig. 5). Following insertion of the forceps, accuracy of the application must be verified. Three criteria should be met (Fig. 6). 1. The sagittal suture should be perpendicular to the plane of the shanks. 2. The posterior fontanelle should be 1 cm above the plane of the shanks. If the distance is greater, the blades are on the face, if less, the head is hyperflexed and the blades should be lowered. In the case of a direct occiput posterior, the fontanelle should be a similar distance below the plane of the shanks. 3. The fenestrations on the blades should be equidistant.
Figure 5. Phantom application permits operator to assess final positioning of the forcep. (From Dennen PC: Forceps Deliveries. Philadelphia, FA Davis, 1989; with permission.)
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Figure 6. Sagittal suture is perpendicular to the plane of the shanks; posterior fontanelle above the plane of the shanks and the fenestrations equidistant. (From Dennen PC: Forceps Deliveries. Philadelphia, FA Davis, 1989; with permission.)
If the occiput is transverse, Kielland or Barton's forceps should be used. The occiput should be identified as well as the relationship of the sagittal suture to an imaginary line that bisects the middle of the maternal pelvis. If the suture is posterior to this line the head is asynclitic; the anterior parietal bone of the fetal head is presenting and Kielland' s forceps should be selected. The anterior blade should be applied first and this may be applied in the "classic" or "wandering" manner. In the former, the blade is placed in an inverted or upside down fashion under the symphysis pubis and behind the bladder, and flipped over. Concern for the integrity of the bladder has lead to decreased use of this method and most select the wandering method. Kielland's forceps have buttons on the handles to indicate the upright position of the forceps and these buttons should be directed toward the occiput. Depending on whether the occiput is right or left, the correct anterior blade is grasped with the handles straight up and applied directly to the posterior portion of the fetal head. Using the fingers of the opposite hand, the blade then is maneuvered or wandered, preferably over the face, into proper position. As the blade approaches the midline in the anterior portion of the pelvis, the handle of the forcep is lowered and this facilitates proper application with the buttons now facing the occiput. The posterior blade is inserted
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then like a shoehorn into the posterior portion of the maternal under fingertip guidance with the button facing the correct direction. The handles then are articulated, and through use of the sliding lock, the asynclitism is corrected. At the completion of the procedure, the handles and finger guides are in line. If the sagittal suture is anterior to the imaginary line, the posterior parietal bone presents and thus, Barton's forceps are the instruments of choice. The anterior blade is wandered similarly as previously described and the hinged portion should come to rest directly on the sagittal suture. The posterior blade has a severe curve, and the handle should rest over the symphysis and almost parallel to the maternal abdomen prior to insertion. Once again, the handles are articulated and the asynclitism is corrected. Insertion of the posterior blade of both the Kielland's and Barton's forceps should be preceded by placement of the operator's whole hand, palm up, in the hollow of the sacrum. Piper's forceps should be applied to the after coming head of the breech infant after delivery of the shoulders and swaddling of the infant's torso and limbs in a towel to prevent injury to the neck and to better expose the head in the vagina (Fig. 7). The operator, kneeling on the floor, should manually flex the head with a finger in the mouth and then insert the blades directly in the space between the fetal head and vaginal walls. Because of the placement of the lock on the left blade, it should be inserted first and this is accomplished best by the assistant's moving of the trunk to the right. The right blade is applied in a similar manner and the handles promptly locked without crossing. Traction is the most commonly used forcep maneuver. Pulling should always follow the principle of axis traction-down and out. The force should be directed at right angles to the station of the head in the pelvis (Fig. 8). If the head is well down in the pelvis, traction may be exerted in a straight outward manner; but if the head occupies a higher station downward, pull on the handles allows the head to egress under the symphysis, and it can be easily extracted with use of the Ritgen's maneuver to control delivery of the head over the perineum. Unless the head is readily visible, traction should coincide with a uterine contraction and the patient's voluntary pushing effort. It is often difficult for the novice to assess the degree of effort needed to accomplish delivery and yet not injure the fetus. By use of a strain gauge attached to the forceps, Pearse9 noted the average amount of tractive force to be 42.3 psi. This equates roughly to the amount of force generated by use of the forearm musculature only. Vigorous tractive efforts using the entire body should be avoided. Simpson and Elliott's forceps are the instruments of choice when traction is required. The separated shanks and long handles of the Simpson's forcep make it ideal for this purpose. Initial attempts should
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Figure 7. Torso and limbs of the infant are displaced to the right and the left blade of the Piper's forcep is inserted to the left side of the maternal pelvis. (From Dennen PC: Forceps Deliveries. Philadelphia, FA Davis, 1989; with permission.)
consist of placing the index finger in the groove of the shanks and pulling gently. If more traction is required, the handles may be grasped at their end. If even more traction be required, the Bill's axis traction handle may be applied to the forceps after articulation but before locking. By pulling down on the bar and observing the directive arrow at the joint formed by the bar and handle, correct amounts of traction in the correct plane may be applied. The DeWeese modification of Simpson's forceps has an axis-traction handle readily adaptable to the left blade of the forceps, and this is an ideal forcep to learn how much and in what direction to apply traction. When using Elliott's forceps, two fingers should grasp the grips located adjacent to the lock. If this fails, the handles may be grasped at the end. If delivery fails to occur with this amount of traction with Elliott's forceps, they should be removed and re-evaluation of the position of the occiput carried out. Rotation of the head arrested in the anterior oblique position is most
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Figure 8. Use of indicator arrow on traction bar helps maintain force at right angle to station of head. (From Dennen PC: Forceps Deliveries. Philadelphia, FA Davis, 1989; with permission.)
often accomplished with the classical instruments. Following proper application, the head may be turned to the direct anterior position immediately, or downward traction may be exerted with the head expected to turn when it encounters perineal muscular resistance. Arrest of the head in other than the anterior oblique position often requires a greater degree of operative skill and the use of an instrument especially designed for this purpose. Kielland's forceps are designed uniquely for dealing with transverse arrest of the head. Proper application is followed by the circumscribing of a narrow arc by the handles of the forcep. This ensures that the toe of the blades will scribe a similar arc which is critical when realizing that they are positioned right under the bladder. It is often helpful to overcorrect on the rotation and take the occiput past the midline to rest on the opposite side. For example, if the head is arrested in the left occiput transverse position, it is best to place the occiput in the right occiput anterior position. Kielland's forceps are poor tractors and when replacing the forceps with one more suitable for extraction, overcorrection coupled with replacement of the posterior blade first will minimize the tendency of the occiput to return to the transverse position. If the head is visible following rotation, there is no need to replace the forceps providing that one is aware of the fact that the handles should never be raised above the horizontal because of the lack of a pelvic curve. To maintain axis traction with Kielland's forceps, downward traction should be exerted with the handles about 45 degrees
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below the horizontal and then raised gradually to the horizontal with further descent of the head. Arrest of the occiput in an oblique posterior or direct posterior position is dealt best with the use of the Leff forceps. Simply constructed and of light weight with short blades and only a slight pelvic curve, they are applied easily in either situation. A traction bar at the end of the handle allows for surprisingly easy and gentle rotation. The Scanzoni maneuver is of historic interest in that it treats the oblique occiput posterior as the opposite occiput anterior; thus, in a head arrested as a right occiput posterior, the posterior blade of a nonfenestrated type forcep, such as the Luikart-Simpson or the Tucker-McLane, is inserted first to the left side of the maternal pelvis. Following application of the anterior blade, the head is flexed firmly and a large arc ("knee to knee") is circumscribed. This is necessary because the toes of the blades are separated and a large external arc ensures that a small internal arc will be scribed. Following rotation, over correction is helpful in this instance also as the forceps are upside down and must be repositioned or replaced by tractors. In all instances described previously, the chin of the presenting face is akin to the occiput and may be dealt with similarly.
ANESTHESIA
The increased availability and widespread patient acceptance of lumbar epidural anesthesia has been associated with an increased incidence of instrumental delivery and an increased incidence of malposition of the fetal head. 8 It is postulated that the increase is due to the loss of the urge to bear down coupled with the relaxation of the pelvic musculature secondary to the anesthetic nerve block. Oxytocin administered at the start of the second stage of labor in patients with an epidural in place has been shown to decrease the overall need for instrumental delivery but not the incidence of malposition. 11 Refinements in anesthetic techniques over the past decade should lead to a decrease in both the need for instrumental delivery and particularly, the incidence of malposition. The addition of a narcotic to the local anesthetic agent has lead to a decrease in strength and total dose of the latter. Fentanyl, an opioid that works at the spinal level in a synergistic fashion with the anesthetic agent, when administered as a dilute solution in continuous fashion, preserves the urge to push and allows the patient to exert effective expulsive effort. Bupivicaine, the most commonly used anesthetic agent, was used formerly in concentrations as high as 0.5% and, currently, in combination with the opioid can be effective when used at strengths as low as 0.125%. On the horizon is the use of a
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combined spinal/ epidural technique in which intrathecal opioid is injected through a spinal needle that, in turn, is placed through an epidural needle. Following injection, the spinal needle is removed and a catheter threaded into the epidural space. The intrathecal administration provides analgesia during labor with sensory block only, and the epidural may be activated for delivery anesthesia. The patient would thus have the urge to push and the ability to do so preserved right up until the time of delivery.
EPISIOTOMY
De Lee's suggestion that episiotomy be combined with low forceps to decrease trauma to the fetal head and maternal perineum has been relatively unquestioned for the past 70 years. Studies in the past 5 years have questioned the use of episiotomy in general and in particular, midline episiotomy and especially when used with forceps.7· 14 Although conceding that the incidence of lacerations is decreased with an episiotomy, the authors have noted an increase in the realm of 2.4-fold and 4-fold in "severe" lacerations consisting of third- and fourth-degree extension. There is no need to perform an episiotomy prior to insertion of forceps and indeed, delivery with forceps can be carried out without an episiotomy. The decision as to the need for and type of episiotomy is made best by the physician during tractive efforts. If the perineum "lengthens" with descent of the head and the fetus is of average size, a midline episiotomy may be performed. The separated shanks of Simpson's forceps added to the diameter of the head would suggest extending the midline episiotomy laterally or performing a median lateral episiotomy initially. Episioproctotomy should be discouraged because of the unpleasant effects that follows the rare breakdown of the repair.
COMPLICATIONS OF FORCEP DELIVERY
Maternal
Thorough exploration of the cervix, vagina, and perineum should be performed following delivery of the placenta and prior to repair of the episiotomy in all patients with forceps application. Complete visualization of the cervix is facilitated by the use of ring forceps to grasp the cervix on the anterior, posterior, and lateral aspects. Inspection of the cervix and adjacent vaginal walls then should be carried out in a
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clockwise manner. Disruption occurs mostly at the 3- and 9-o' clock positions and unless bleeding is present or the defect is lengthy, repair is not required. Careful inspection of the posterior fornix is indicated especially when Kielland or Barton's forceps are used because of the manner of application of the posterior blades. Punctate tears of the lateral wall are often present if rotation from an oblique occiput posterior has occurred. Deviation from the plane of axis traction will result in sulcus tears when Simpson's forceps are used for traction. Periurethral lacerations are found commonly and if the urethra is intact and there is no bleeding, they are best left alone. If bleeding persists and the fundus is firm, the lower uterine segment should be explored manually. Prompt recognition of bladder or rectal injury is imperative. If there be any indication of impairment of the posterior wall of the bladder, contrast material should be instilled through a catheter. If leakage occurs, the site should be repaired using the principles of fistula repair. Lacerations that disrupt the anal sphincter are associated with incontinence of flatus or stool in up to 40% of cases,6 whereas those that involve the rectal mucosa carry the added risks of infection, wound breakdown, and fistula formation. Anal endosonography has been used to detect mechanical and neurologic damage to the internal and external anal sphincters. Sultan13 has shown that clinical examination revealed a 3% incidence of sphincter damage in primiparous patients, whereas anal endosonography showed 33% to have sustained sphincter damage. Careful inspection of the sphincter may reveal capsular defects and thus, reinforcing sutures should be placed. If a complete third-degree tear is evident reapproximation of the muscle fibers with closure of the anterior and posterior capsule should be carried out. The presence of a fourthdegree laceration calls for meticulous closure of the defect preferably in two layers-reapproximation of the sphincter and layered closure of the rectovaginal fascia to build up the perineal body and ensure continence.
Neonatal
Erythema and ecchymosis of the skin or the face of a newborn, although unsightly at times, do not necessarily reflect on the skill of the physician or the amount of traction used. Retinal hemorrhage in newborns has been noted to be more common with spontaneous vaginal delivery than with forcep use. 5 Cephalhematoma, subdural and intracerebral hemorrhage may result from both improper forcep application and undue tractive efforts. Physiologic caput formation should subside by 48 to 72 hours, and any persistent asymmetric swelling of the scalp should be investigated with ultrasonography and a skull radiograph to
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rule out an underlying fracture. Persistent irritability or other signs of increased intracranial pressure should be investigated with computed tomography. Although controversial, the use of forceps in delivering infants at risk for intraventricular hemorrhage may be protective. 12 Cranial nerve injury has been ascribed to forcep use. Improper choice of instruments or application to a long, molded head may compress the seventh cranial nerve and lead to facial palsy. The sixth cranial nerve may be compressed also as it crosses the petrous portion of the temporal bone, and thus, a lateral rectus muscle palsy results. The finding of a contralateral orbital depression may serve as a clue to this finding and would suggest improper application. Neonatal acid-base studies comparing infants delivered using forceps with a control group of spontaneously delivered babies have shown differences in pH and base deficits in the instrumental groups. Critical analysis suggests that these differences are related more to the duration of the second stage of labor than to the type of delivery. Of import is the fact that there is no convincing evidence at present to incriminate properly conducted forcep delivery per se in the causation of cerebral palsy, seizure disorders, or behavioral impairment.
CONCLUSION
Because of the increasing emphasis on methods of prepared childbirth, the tendency to decreased use of forceps will continue in the future. It is essential that teaching of these methods not inculcate in the mother the sense of failure should forceps be required for valid maternal or fetal indication. On the other hand, the increasing popularity of conduction of anesthesia delivery may be reflected by a corresponding increase in forceps deliveries. Obstetricians should become familiar, therefore, with the advantages inherent in the different types of forceps available and gain experience in their use. Present day obstetrics still includes a place for instrumental delivery, subject to well defined indications and conditions.
References 1. American College of Obstetrics and Gynecologists. Manual of standards in obstetricgynecologic practice, ed 2. Washington, DC, American College of Obstetricians and Gynecologists, 1965 2. American College of Obstetricians. Obstetric forceps. ACOG committee opinion No. 71. Washington, DC, American College of Obstetricians and Gynecologists, 1989 3. Dill L: The Obstetrical Forceps. Springfield, IL, Charles C Thomas, 1953
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4. Douglas L, Kaltreider D: Trial forceps. American Journal of Obstetrics and Gynecology 65:889, 1953 5. Egge K, Lyng G, Maltau J: Effect of instrumental delivery on the frequency and severity of retinal hemorrhages in the newborn. Acta Obstet Gynecol Scand 60:153, 1981 6. Haadem K, Dahlstrom JA, Lingh, et al: Anal sphincter function after delivery rupture. Obstet Gynecol 70:53, 1987 7. Helwig J, Thorp J, Bowes W: Does midline episiotomy increase the risk of third- and fourth-degree lacerations in operative vaginal deliveries? Obstet Gynecol 82:276, 1993 8. Hoult I, MacLennan A, Carrie L: Lumbar epidural analgesia in labor: Relation to fetal malposition and instrumental delivery. BMJ 1:14, 1977 9. Pearse W: Electronic recording of forcep deliveries. Am J Obstet Gynecol 86:43, 1963 10. Ramin S, Little B, Gilstap L: Survey of forceps deliveries in North America in 1990. Obstet Gynecol 81:307, 1993 11. Saunders N, Spiby H, Gilbert L, et al: Oxytocin infusion during second stage of labor in primiparous women using epidural analgesia: A randomized double blind placebo controlled group. BMJ 299:1423, 1989 12. Shaver D, Eada H, Korones S: Early and late intraventricular hemorrhage: The role of obstetric factors. Obstet Gynecol 80:831, 1992 13. Sultan A, Kamm M, Hudson C, et al: Anal-sphincter disruption during vaginal delivery. N Engl J Med 329:1905, 1993 14. Walker M, Farine D, Rolbin S, et al: Epidural anesthesia, episiotomy and obstetric laceration. Obstet Gynecol 77:668, 1991
Address reprint requests to James P. Thompson, MD Notch View Office Park 1035 Route 46 East Clifton, NJ 07013
0095-5108/95 $0.00 + .20
DELIVERIES James P. Thompson, MD
The increased incidence of cesarean sections and the tendency to manage labor more actively in recent years has caused many to reevaluate the role of forceps deliveries in the modern day practice of obstetrics. On the one hand, cesarean sections done early in labor negate the consideration of forcep use. On the other hand, higher-dose oxytocin stimulation is continued often until spontaneous delivery of the vertex occurs. Coupled with these trends in labor management is the realization that for the past two decades there has been an apparent reduction in the importance of forceps deliveries in many of the obstetric residency training programs. In some programs, the use of forceps is barred entirely, thus, depriving residents of gaining an awareness of both the potential benefits and risks of a previously thought useful obstetric practice. Efforts to curtail the rising cesarean section rate include more liberal use of oxytocin, more concentrated nursing attention during labor, and a reaffirmation of vaginal operative skills. It is appropriate, therefore, to review the principles that have guided our use of forceps in the past.
HISTORICAL REVIEW
The use of forceps dates back to ancient times. One thousand years before the birth of Christ, Hindu writers described a knife and hook that were used in difficult labors to destroy the fetal head and extract the
From the Department of Obstetrics and Gynecology, University of Medicine and Dentistry of New Jersey, Newark, New Jersey
CLINICS IN PERINATOLOGY VOLUME 22 • NUMBER 4 • DECEMBER 1995
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fetus. In 400 BC, Hippocrates wrote of delivery by traction. Avicenna, a Persian physician who lived from 980 to 1037 AD, demonstrated their use and Albucasis prepared an illustrated series on forceps, including an instrument with teeth on their inner surface to obtain a better hold on the fetal head. The word forceps is derived from the Latin formus meaning instrument and capio meaning to seize according to Dill. 3 The concept of forceps as we know them today dates back to the late 16th century when Peter Chamberlen introduced the first instrument to be used for the delivery of a living infant. Prior use of the forceps was limited mostly to destructive procedures followed by extraction. Chamberlen's design was remarkably simple and it included a pair of fenestrated blades approximately 12 in long that crossed outside of the vagina. The blades were designed with a cephalic curve to better grasp the fetal head. Contributing to the lore of obstetrics, it is said that succeeding generations of the Chamberlen family kept the design of this instrument a closely guarded secret for over a century. In 1745, Smellie advocated application to the fetal head with the posterior fontanelle as the point of reference rather than the previously practiced pelvic application. Soon after, Levret introduced an instrument with a pelvic curve that included also a wing nut type of articulation, later referred to as the French lock. In the United States, the first historical account of the use of forceps was that of James of Philadelphia in 1812. Simpson developed an instrument with a long cephalic curve to the blades and an interlocking handle in 1848. A decade later, Elliott devised a forcep that was smaller and lighter and had a rounded cephalic curve that was thought to be better adapted to unmolded heads. Both of these prototypes, virtually unchanged from their original designs over 100 years ago, are used on a daily basis in delivery units today. In 1877, Tarnier using principles of physics espoused by Pajot and descriptions of pelvic anatomy by Carus introduced the principle of axis traction. Significant changes in forcep design and versatility came about early in the 20th century. In 1915, Kielland introduced an instrument especially for rotating the head when arrested in the transverse or posterior position. The absence of a pelvic curve and the creation of a sliding lock on the handles for correction of the asynclitism that frequently accompanies transverse position of the head have made Kielland forceps especially useful for rotation. The first truly innovative contribution of an American to forcep design was that of Barton, who in 1925, designed an instrument to resolve transverse arrest and asynclitism that included a hinged anterior blade, sliding lock, and traction bar. During the same time, forceps designed to deliver the after coming head in a breech presentation were introduced by Piper. Increasing use of the prototypic instruments with fenestrated blades lead to the observation
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that compression of the vaginal wall between the openings lead to lacerations and, in 1937, Luikart modified the blades of the standard types of forceps by obliterating the fenestrated portion. He incorporated hollowed out indentures on the inner surfaces of the blades to facilitate grasping of the fetal head and decrease pressure marks on the face of the newborn. The surge of interest in the use of forceps occurred after De Lee's assertion in 1920 that the prophylactic use of forceps coupled with an episiotomy decreased trauma to maternal tissue and protected the fetal skull and brain. Although scientific data documenting the merits of his claim are lacking, the incidence of forceps use exceeded 50% in many institutions during the next 20 years. The introduction of antibiotics, safer use of blood transfusions and anesthetic agents, and the liberal use of cesarean sections have resulted in a marked decrease in the use of forceps currently. Innovative design, modification, and refinement have lead to the description of over 700 types of obstetric forceps. Save for the four or five basic instruments, the remainder are noteworthy only from the historical standpoint.
CLASSIFICATION
The increasing use of forceps brought about the need to describe accurately their mode of application. The level of the fetal head in the maternal pelvis and the location of the sagittal suture and posterior fontanelle of the fetal head at the time of application provide the basis for classification of forceps operations. In an attempt to standardize the nomenclature describing forceps use, the American College of Obstetricians and Gynecologists defined outlet, mid and high forceps in 1965. 1 The latitude between outlet and mid forceps created a good deal of confusion in that most applications did not meet the requirements of outlet forceps nor did they imply the necessary surgical skills or legal connotations of mid forceps; thus, the majority of forceps applications were classified as "low" although that definition was not included in the 1965 definition. In addition, the use of high forceps soon became unacceptable because of the high incidence of maternal and neonatal morbidity that often accompanied their use. In an attempt to clarify this disparity, the ACOG formulated a new definition that was introduced in 1989. 2 This is essentially a three level classification marked by the relationship between the leading bony portion of the fetal head (not caput formation) and the ischial spines of the maternal pelvis. The newer definition does not give special preference to the position of the posterior fontanelle; thus, delivery of the fetal head
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presenting as an occiput posterior from the + 2 station in the posterior position is considered now a low forceps, whereas it was previously a mid forceps operation. Comparison of the old and new definitions is shown in Table l. A recent survey of residency training programs revealed that 99% of program directors were familiar with the new definitions, but 20% of them did not use them when defining forceps operations. 10
PREREQUISITES
Prior to the application of forceps, there are certain conditions that must be met. Thorough knowledge of the anatomic characteristics of the maternal pelvis is determined best by a manual examination. Correct diagnosis of the position of the fetal head as marked by the locale of the posterior fontanelle should be made. This determination is often made
Table 1. AMERICAN COLLEGE OF OBSTETRICIANS AND GYNECOLOGISTS DEFINITIONS OF FORCEPS DELIVERIES
Classic definitions Outlet forceps Scalp visible at introitus without separating labia Skull has reached pelvic floor Sagittal suture is in anteroposterior diameter of pelvis Midforceps Head engaged Conditions of outlet forceps not met Artificial rotation High forceps Application of forceps before engagement of fetal vertex New definitions Outlet forceps Scalp visible at introitus without separating labia Skull has reached pelvic floor Sagittal suture is in anteroposterior diameter or right occipitoanterior, left occipitoanterior, occipitoposterior Fetal head at or on the perineum Rotation cannot exceed 45 degrees Low forceps Leading point of skull 2: + 2 Rotation s:: 45 degrees Rotation > 45 degrees Midforceps Head engaged Leading point of skull is above + 2 Adapted from American College of Obstetricians and Gynecologists. Operative vaginal delivery. ACOG Technical Bulletin No. 196. Washington, DC, American College of Obstetricians and Gynecologists, 1994, p 2; with permission.
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best in the later part of the first stage of labor prior to the occurrence of molding which often obscures the bony landmarks. Triangular in shape, the posterior fontanelle is formed by the union of the sagittal suture and the two lambdoidal sutures. The anterior fontanelle is formed by the union of the sagittal suture with the two coronal and the frontal sutures. Palpation and outlining of the posterior fontanelle is the desired method of determining the exact position, but in instances in which it is difficult, location of the anterior fontanelle coupled with palpation of the orbit or an ear will suffice. The fetal head must be engaged. Currently, this implies that the leading bony point of the fetal skull has reached the level of the ischial spines. If the face is presenting, the chin must be at the level of the spines. The cervix must be dilated and retracted completely. Often with oblique positions and direct occiput posteriors, the cervix will be dilated completely but not retracted completely. To prevent trauma to the cervix, it must be "gently retractable" prior to application of the forceps. Membranes must be ruptured. Catheterization of the bladder and manual compression of the posterior vaginal wall to empty the rectum will help decrease trauma to adjacent maternal organs. The patient should be positioned well down on the delivery table with the buttocks overhanging by at least 1 in so that proper axis traction can be maintained. Although not essential, an episiotomy helps decrease soft tissue resistance and limits the amount of traction necessary to deliver the fetal head. As with any surgical procedure, adequate anesthesia must be used to diminish maternal anxiety and pain. Pudendal block often will suffice for outlet forceps in the well-prepared patient. Low and mid forcep operations often require conduction anesthesia in the form of a saddle block or epidural. On rare occasions, inhalation anesthesia may be required and it is essential that an experienced anesthetist be present and that intubation be considered to prevent aspiration of gastric contents. Familiarity with the types of forceps available is essential. There is no universal forcep and the days of "learning one instrument and using it well" are over. Refinements in design have resulted in the construction of instruments with special features for dealing with variations in pelvic anatomy and positions of the fetal head. Electronic fetal monitoring techniques should be continued right up until delivery of the head. Placement of an internal scalp lead will permit this and aside from the minor annoyance of the electrode wire, will often prove reassuring and will decrease haste in extracting. Biochemical modes should be available also. Personnel experienced in neonatal resuscitation should be present in the delivery room for anything other than an outlet forcep delivery. A list of the prerequisites appears in Table 2.
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Table 2. PREREQUISITES FOR THE USE OF FORCEPS
Knowledge of pelvic anatomy Awareness of position of fetal head Cervix completely dilated Membranes ruptured Bladder, bowel empty
Familiarity with types of forceps Surgical environment Proper anesthesia Suitable monitoring techniques Facility for newborn resuscitation
INDICATIONS
Maternal indications for the use of forceps include the inability of the mother to exert adequate propulsive efforts owing to exhaustion or the presence of a conduction anesthetic. Prolongation of the second stage of labor is no longer limited to 2 hours if fetal heart rate monitoring techniques indicate no distress and progress in descent continues. Edema of the vagina and vulva will often be time-limiting factors but in their absence and with no signs of fetal distress, the second stage of labor may continue for a reasonable length of time beyond 2 hours. Medical complications of pregnancy that tax maternal reserve may provide indication for the use of forceps. Shortening of the second stage of labor is beneficial often to patients with heart disease, neurologic disease with increased intracranial pressure, and pregnancy-induced hypertension. Obstetric complications of pregnancy such as abruptio placentae may warrant early intervention. Fetal indications for the use of forceps include failure of further descent of the fetal head already well down in the pelvis, rotatory arrest, and selected malpresentations. The pliability of the fetal head leads to molding and when the head is at an advanced station in the pelvis and the decision is made that spontaneous delivery is unlikely in the next 30 minutes, forceps are best applied prior to the obliteration of bony landmarks and before the head is elongated to the degree that the toes of the forceps will not obtain the desired purchase point. Fetal heads that arrest in the oblique or transverse diameter are rotated best to the anterior position to facilitate spontaneous delivery or extraction. The persistence of an occiput posterior position often leads to deflexion of the head and creates the need for increased propulsive effort. Rotation to the occiput anterior position frequently leads to further descent and spontaneous delivery. Fetal distress, usually in the form of bradycardia, is often best handled by delivery with forceps rather than by allowing labor to continue or resorting to emergency cesarean section. It is mandatory that all of the prerequisites be met prior to the application of forceps for the latter indication.
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CONTRAINDICATIONS
Failure to meet the prerequisites for the use of forceps implies that another route of delivery be considered. The inability to evaluate adequately the maternal pelvis, such as may happen when confronted with a patient in labor and a history of previous trauma to the pelvis or the finding of an inadequate pelvis on manual examination, are contraindications. Doubts about the position of the fetal head or the presence of macrosomia should lead to exclusion of forceps as the route of delivery. The cervix should be dilated completely because the use of Duhrssens incisions is indicated rarely, if ever. Lack of familiarity with the various types of forceps and their potential for harm with improper use should also mitigate against their use. Controversy exists over the concepts and use of the terms "trial of forceps" and "failed forceps." Douglas and Kaltreider4 introduced the concept of trial of forceps and stressed the intent of the operator in carrying out the planned procedure. If an honest attempt is made to apply forceps to rotate or extract and resistance met with cessation of efforts before the occurrence of maternal or fetal injury, there is a place for trial of forceps. All too often, this designation is applied to vigorous attempts to deliver without success and a true failure of forcep delivery results. The semantic differentiation between the terms is often retrospective and confusing. Errors in judgment in applying the forceps and attempting delivery should not be confounded by the incurrence of maternal or fetal injury.
FORCEP DESIGN
Forceps are the primary surgical instrument of the obstetrician. As such, their use should be limited to the appropriate area-sterile environment, ample light source, and room to work-and governed by the operator's knowledge of the instrument. All forceps consist of blades, shanks, handles, and locks. The blades are the portion that is applied directly to the fetal head. Most are fenestrated. The pelvic curve of the forceps lies in the relationship of the blades to the shanks. To best appreciate the extent of the pelvic curve, the forceps are placed on a flat surface and the extent to which the tips of the blades rise above the horizontal plane defines the pelvic curve. This is designed to correspond to the curve of the maternal pelvis. The cephalic curve is defined by the rounded portion of the blades (Fig. 1). The Simpson's forcep has a long, tapered cephalic curve designed to use with molded heads, especially of the type found in primiparous patients. DeWeese and Tarniers' forceps are variants of the Simpson's forcep. The Elliott's forcep has a
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Figure 1. Illustration of DeWeese's forceps (left), Simpson's forceps (center), and Elliot's forceps (right).
Figure 2. The French lock is represented on the forcep to the left and the English lock is found on the forcep to the right.
Figure 3. Leffs forceps. Note the long, tapered, cephalic curve, and the bar at the end to facilitate rotation.
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shorter, rounded cephalic curve for use in multiparous patients who have not had a prolonged second stage and in whom molding of the fetal head would be unusual. Bayley-Williamson and Tucker-Mclane forceps are variants of the prototype with the latter also having a nonfenestrated blade that makes it particularly useful for rotation. The shanks of the forcep connect the blades to the handle. Most cross outside of the vagina after insertion of both blades, but Simpson's forceps remain separated right up to the point of union with the handles. Elliott's forceps have shanks that are crossed in their entirety. Parallel forceps such as those Shute designed have noncrossing shanks, and use is dependent on the maintenance of parallelism throughout the length of the forcep. The length of the shank determines the extent of the degree of traction that may be obtained. The longer the shank, the greater the traction. Handles are hollowed out usually and contain finger grips to assist with traction. Although they vary in length, a good general rule is to grasp the handles as close to their shanks as possible to decrease the amount of traction. Conversely, if more traction is required for delivery, a longhandled forcep grasped at the end will provide for more traction. Locks are located at the intersection of the shanks and are designed to prevent slippage following correct application. Terminology describing the types of locks is based on the country of origin (Fig. 2). The English lock, by far the most common, has a fixed notch on one blade to which the other blade is articulated following application. Simpson's and Elliott's forceps both have locks of this type. The French lock consists of an adjustable screw and wing nut located on one shank that fits into a groove on the other. Useful modifications of forceps include changes in each of the components designed to meet the clinical variations encountered. Leff forceps have a long cephalic curve, small pelvic curve, and a small bar at the end of the handle all designed to facilitate rotation (Fig. 3). Kielland's forceps have virtually no pelvic curve to the blades and a sliding lock that allows for correction of asynclitism prior to rotation. Barton's forceps have a hinged anterior blade that is flexible over an arc of 90 degrees and a traction bar. By exerting downward traction on the bar following application in the transverse position, the vector forces are resolved through the hinged blade so that rotation occurs when the vertex encounters resistance from the levator musculature. Piper's forceps are long and springy with their pelvic curve designed for flexion and extraction of the aftercoming head. FORCEP MANEUVERS
Proper application of the forceps must precede the two principal purposes for forcep use which are traction and rotation. Using the
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posterior fontanelle or occiput as the point of reference, the blades are applied to the lateral portions of the fetal head. If the occiput is directly anterior, the left blade of the forceps is grasped in the operator's left hand and applied to the left side of the maternal pelvis. The operator's right hand should be inserted into the vagina prior to the forcep blade, and the tips of the fingers should guide the toe of the blade into position while the thumb should rest on the heel of the blade (Fig. 4). An assistant should hold firmly the handle of the forcep in place while the operator inserts his left hand into the vagina and guides the right blade to the right side of the fetal head on the right side of the maternal pelvis. If the occiput is positioned obliquely, the posterior blade should be inserted first. In the case of left occiput anterior, application is identical to occiput anterior. If the occiput is to the right of the midline, the right blade should be inserted to the right side of the maternal pelvis to provide support while the left blade is inserted. The left blade is positioned higher on the fetal head and the handles must be crossed over
Figure 4. Finger tips are used to guide the toe of the blade into place. (From Dennen PC: Forceps Deliveries. Philadelphia, FA Davis, 1989; with permission.)
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one another to lock When the occiput is directly posterior, forceps application is identical to that of occiput anterior. Prior to insertion of the forceps, it helps to make a "phantom application" in which the forceps are aligned outside of the vagina to correspond with the position of the fetal head (Fig. 5). Following insertion of the forceps, accuracy of the application must be verified. Three criteria should be met (Fig. 6). 1. The sagittal suture should be perpendicular to the plane of the shanks. 2. The posterior fontanelle should be 1 cm above the plane of the shanks. If the distance is greater, the blades are on the face, if less, the head is hyperflexed and the blades should be lowered. In the case of a direct occiput posterior, the fontanelle should be a similar distance below the plane of the shanks. 3. The fenestrations on the blades should be equidistant.
Figure 5. Phantom application permits operator to assess final positioning of the forcep. (From Dennen PC: Forceps Deliveries. Philadelphia, FA Davis, 1989; with permission.)
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Figure 6. Sagittal suture is perpendicular to the plane of the shanks; posterior fontanelle above the plane of the shanks and the fenestrations equidistant. (From Dennen PC: Forceps Deliveries. Philadelphia, FA Davis, 1989; with permission.)
If the occiput is transverse, Kielland or Barton's forceps should be used. The occiput should be identified as well as the relationship of the sagittal suture to an imaginary line that bisects the middle of the maternal pelvis. If the suture is posterior to this line the head is asynclitic; the anterior parietal bone of the fetal head is presenting and Kielland' s forceps should be selected. The anterior blade should be applied first and this may be applied in the "classic" or "wandering" manner. In the former, the blade is placed in an inverted or upside down fashion under the symphysis pubis and behind the bladder, and flipped over. Concern for the integrity of the bladder has lead to decreased use of this method and most select the wandering method. Kielland's forceps have buttons on the handles to indicate the upright position of the forceps and these buttons should be directed toward the occiput. Depending on whether the occiput is right or left, the correct anterior blade is grasped with the handles straight up and applied directly to the posterior portion of the fetal head. Using the fingers of the opposite hand, the blade then is maneuvered or wandered, preferably over the face, into proper position. As the blade approaches the midline in the anterior portion of the pelvis, the handle of the forcep is lowered and this facilitates proper application with the buttons now facing the occiput. The posterior blade is inserted
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then like a shoehorn into the posterior portion of the maternal under fingertip guidance with the button facing the correct direction. The handles then are articulated, and through use of the sliding lock, the asynclitism is corrected. At the completion of the procedure, the handles and finger guides are in line. If the sagittal suture is anterior to the imaginary line, the posterior parietal bone presents and thus, Barton's forceps are the instruments of choice. The anterior blade is wandered similarly as previously described and the hinged portion should come to rest directly on the sagittal suture. The posterior blade has a severe curve, and the handle should rest over the symphysis and almost parallel to the maternal abdomen prior to insertion. Once again, the handles are articulated and the asynclitism is corrected. Insertion of the posterior blade of both the Kielland's and Barton's forceps should be preceded by placement of the operator's whole hand, palm up, in the hollow of the sacrum. Piper's forceps should be applied to the after coming head of the breech infant after delivery of the shoulders and swaddling of the infant's torso and limbs in a towel to prevent injury to the neck and to better expose the head in the vagina (Fig. 7). The operator, kneeling on the floor, should manually flex the head with a finger in the mouth and then insert the blades directly in the space between the fetal head and vaginal walls. Because of the placement of the lock on the left blade, it should be inserted first and this is accomplished best by the assistant's moving of the trunk to the right. The right blade is applied in a similar manner and the handles promptly locked without crossing. Traction is the most commonly used forcep maneuver. Pulling should always follow the principle of axis traction-down and out. The force should be directed at right angles to the station of the head in the pelvis (Fig. 8). If the head is well down in the pelvis, traction may be exerted in a straight outward manner; but if the head occupies a higher station downward, pull on the handles allows the head to egress under the symphysis, and it can be easily extracted with use of the Ritgen's maneuver to control delivery of the head over the perineum. Unless the head is readily visible, traction should coincide with a uterine contraction and the patient's voluntary pushing effort. It is often difficult for the novice to assess the degree of effort needed to accomplish delivery and yet not injure the fetus. By use of a strain gauge attached to the forceps, Pearse9 noted the average amount of tractive force to be 42.3 psi. This equates roughly to the amount of force generated by use of the forearm musculature only. Vigorous tractive efforts using the entire body should be avoided. Simpson and Elliott's forceps are the instruments of choice when traction is required. The separated shanks and long handles of the Simpson's forcep make it ideal for this purpose. Initial attempts should
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Figure 7. Torso and limbs of the infant are displaced to the right and the left blade of the Piper's forcep is inserted to the left side of the maternal pelvis. (From Dennen PC: Forceps Deliveries. Philadelphia, FA Davis, 1989; with permission.)
consist of placing the index finger in the groove of the shanks and pulling gently. If more traction is required, the handles may be grasped at their end. If even more traction be required, the Bill's axis traction handle may be applied to the forceps after articulation but before locking. By pulling down on the bar and observing the directive arrow at the joint formed by the bar and handle, correct amounts of traction in the correct plane may be applied. The DeWeese modification of Simpson's forceps has an axis-traction handle readily adaptable to the left blade of the forceps, and this is an ideal forcep to learn how much and in what direction to apply traction. When using Elliott's forceps, two fingers should grasp the grips located adjacent to the lock. If this fails, the handles may be grasped at the end. If delivery fails to occur with this amount of traction with Elliott's forceps, they should be removed and re-evaluation of the position of the occiput carried out. Rotation of the head arrested in the anterior oblique position is most
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Figure 8. Use of indicator arrow on traction bar helps maintain force at right angle to station of head. (From Dennen PC: Forceps Deliveries. Philadelphia, FA Davis, 1989; with permission.)
often accomplished with the classical instruments. Following proper application, the head may be turned to the direct anterior position immediately, or downward traction may be exerted with the head expected to turn when it encounters perineal muscular resistance. Arrest of the head in other than the anterior oblique position often requires a greater degree of operative skill and the use of an instrument especially designed for this purpose. Kielland's forceps are designed uniquely for dealing with transverse arrest of the head. Proper application is followed by the circumscribing of a narrow arc by the handles of the forcep. This ensures that the toe of the blades will scribe a similar arc which is critical when realizing that they are positioned right under the bladder. It is often helpful to overcorrect on the rotation and take the occiput past the midline to rest on the opposite side. For example, if the head is arrested in the left occiput transverse position, it is best to place the occiput in the right occiput anterior position. Kielland's forceps are poor tractors and when replacing the forceps with one more suitable for extraction, overcorrection coupled with replacement of the posterior blade first will minimize the tendency of the occiput to return to the transverse position. If the head is visible following rotation, there is no need to replace the forceps providing that one is aware of the fact that the handles should never be raised above the horizontal because of the lack of a pelvic curve. To maintain axis traction with Kielland's forceps, downward traction should be exerted with the handles about 45 degrees
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below the horizontal and then raised gradually to the horizontal with further descent of the head. Arrest of the occiput in an oblique posterior or direct posterior position is dealt best with the use of the Leff forceps. Simply constructed and of light weight with short blades and only a slight pelvic curve, they are applied easily in either situation. A traction bar at the end of the handle allows for surprisingly easy and gentle rotation. The Scanzoni maneuver is of historic interest in that it treats the oblique occiput posterior as the opposite occiput anterior; thus, in a head arrested as a right occiput posterior, the posterior blade of a nonfenestrated type forcep, such as the Luikart-Simpson or the Tucker-McLane, is inserted first to the left side of the maternal pelvis. Following application of the anterior blade, the head is flexed firmly and a large arc ("knee to knee") is circumscribed. This is necessary because the toes of the blades are separated and a large external arc ensures that a small internal arc will be scribed. Following rotation, over correction is helpful in this instance also as the forceps are upside down and must be repositioned or replaced by tractors. In all instances described previously, the chin of the presenting face is akin to the occiput and may be dealt with similarly.
ANESTHESIA
The increased availability and widespread patient acceptance of lumbar epidural anesthesia has been associated with an increased incidence of instrumental delivery and an increased incidence of malposition of the fetal head. 8 It is postulated that the increase is due to the loss of the urge to bear down coupled with the relaxation of the pelvic musculature secondary to the anesthetic nerve block. Oxytocin administered at the start of the second stage of labor in patients with an epidural in place has been shown to decrease the overall need for instrumental delivery but not the incidence of malposition. 11 Refinements in anesthetic techniques over the past decade should lead to a decrease in both the need for instrumental delivery and particularly, the incidence of malposition. The addition of a narcotic to the local anesthetic agent has lead to a decrease in strength and total dose of the latter. Fentanyl, an opioid that works at the spinal level in a synergistic fashion with the anesthetic agent, when administered as a dilute solution in continuous fashion, preserves the urge to push and allows the patient to exert effective expulsive effort. Bupivicaine, the most commonly used anesthetic agent, was used formerly in concentrations as high as 0.5% and, currently, in combination with the opioid can be effective when used at strengths as low as 0.125%. On the horizon is the use of a
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combined spinal/ epidural technique in which intrathecal opioid is injected through a spinal needle that, in turn, is placed through an epidural needle. Following injection, the spinal needle is removed and a catheter threaded into the epidural space. The intrathecal administration provides analgesia during labor with sensory block only, and the epidural may be activated for delivery anesthesia. The patient would thus have the urge to push and the ability to do so preserved right up until the time of delivery.
EPISIOTOMY
De Lee's suggestion that episiotomy be combined with low forceps to decrease trauma to the fetal head and maternal perineum has been relatively unquestioned for the past 70 years. Studies in the past 5 years have questioned the use of episiotomy in general and in particular, midline episiotomy and especially when used with forceps.7· 14 Although conceding that the incidence of lacerations is decreased with an episiotomy, the authors have noted an increase in the realm of 2.4-fold and 4-fold in "severe" lacerations consisting of third- and fourth-degree extension. There is no need to perform an episiotomy prior to insertion of forceps and indeed, delivery with forceps can be carried out without an episiotomy. The decision as to the need for and type of episiotomy is made best by the physician during tractive efforts. If the perineum "lengthens" with descent of the head and the fetus is of average size, a midline episiotomy may be performed. The separated shanks of Simpson's forceps added to the diameter of the head would suggest extending the midline episiotomy laterally or performing a median lateral episiotomy initially. Episioproctotomy should be discouraged because of the unpleasant effects that follows the rare breakdown of the repair.
COMPLICATIONS OF FORCEP DELIVERY
Maternal
Thorough exploration of the cervix, vagina, and perineum should be performed following delivery of the placenta and prior to repair of the episiotomy in all patients with forceps application. Complete visualization of the cervix is facilitated by the use of ring forceps to grasp the cervix on the anterior, posterior, and lateral aspects. Inspection of the cervix and adjacent vaginal walls then should be carried out in a
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clockwise manner. Disruption occurs mostly at the 3- and 9-o' clock positions and unless bleeding is present or the defect is lengthy, repair is not required. Careful inspection of the posterior fornix is indicated especially when Kielland or Barton's forceps are used because of the manner of application of the posterior blades. Punctate tears of the lateral wall are often present if rotation from an oblique occiput posterior has occurred. Deviation from the plane of axis traction will result in sulcus tears when Simpson's forceps are used for traction. Periurethral lacerations are found commonly and if the urethra is intact and there is no bleeding, they are best left alone. If bleeding persists and the fundus is firm, the lower uterine segment should be explored manually. Prompt recognition of bladder or rectal injury is imperative. If there be any indication of impairment of the posterior wall of the bladder, contrast material should be instilled through a catheter. If leakage occurs, the site should be repaired using the principles of fistula repair. Lacerations that disrupt the anal sphincter are associated with incontinence of flatus or stool in up to 40% of cases,6 whereas those that involve the rectal mucosa carry the added risks of infection, wound breakdown, and fistula formation. Anal endosonography has been used to detect mechanical and neurologic damage to the internal and external anal sphincters. Sultan13 has shown that clinical examination revealed a 3% incidence of sphincter damage in primiparous patients, whereas anal endosonography showed 33% to have sustained sphincter damage. Careful inspection of the sphincter may reveal capsular defects and thus, reinforcing sutures should be placed. If a complete third-degree tear is evident reapproximation of the muscle fibers with closure of the anterior and posterior capsule should be carried out. The presence of a fourthdegree laceration calls for meticulous closure of the defect preferably in two layers-reapproximation of the sphincter and layered closure of the rectovaginal fascia to build up the perineal body and ensure continence.
Neonatal
Erythema and ecchymosis of the skin or the face of a newborn, although unsightly at times, do not necessarily reflect on the skill of the physician or the amount of traction used. Retinal hemorrhage in newborns has been noted to be more common with spontaneous vaginal delivery than with forcep use. 5 Cephalhematoma, subdural and intracerebral hemorrhage may result from both improper forcep application and undue tractive efforts. Physiologic caput formation should subside by 48 to 72 hours, and any persistent asymmetric swelling of the scalp should be investigated with ultrasonography and a skull radiograph to
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rule out an underlying fracture. Persistent irritability or other signs of increased intracranial pressure should be investigated with computed tomography. Although controversial, the use of forceps in delivering infants at risk for intraventricular hemorrhage may be protective. 12 Cranial nerve injury has been ascribed to forcep use. Improper choice of instruments or application to a long, molded head may compress the seventh cranial nerve and lead to facial palsy. The sixth cranial nerve may be compressed also as it crosses the petrous portion of the temporal bone, and thus, a lateral rectus muscle palsy results. The finding of a contralateral orbital depression may serve as a clue to this finding and would suggest improper application. Neonatal acid-base studies comparing infants delivered using forceps with a control group of spontaneously delivered babies have shown differences in pH and base deficits in the instrumental groups. Critical analysis suggests that these differences are related more to the duration of the second stage of labor than to the type of delivery. Of import is the fact that there is no convincing evidence at present to incriminate properly conducted forcep delivery per se in the causation of cerebral palsy, seizure disorders, or behavioral impairment.
CONCLUSION
Because of the increasing emphasis on methods of prepared childbirth, the tendency to decreased use of forceps will continue in the future. It is essential that teaching of these methods not inculcate in the mother the sense of failure should forceps be required for valid maternal or fetal indication. On the other hand, the increasing popularity of conduction of anesthesia delivery may be reflected by a corresponding increase in forceps deliveries. Obstetricians should become familiar, therefore, with the advantages inherent in the different types of forceps available and gain experience in their use. Present day obstetrics still includes a place for instrumental delivery, subject to well defined indications and conditions.
References 1. American College of Obstetrics and Gynecologists. Manual of standards in obstetricgynecologic practice, ed 2. Washington, DC, American College of Obstetricians and Gynecologists, 1965 2. American College of Obstetricians. Obstetric forceps. ACOG committee opinion No. 71. Washington, DC, American College of Obstetricians and Gynecologists, 1989 3. Dill L: The Obstetrical Forceps. Springfield, IL, Charles C Thomas, 1953
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4. Douglas L, Kaltreider D: Trial forceps. American Journal of Obstetrics and Gynecology 65:889, 1953 5. Egge K, Lyng G, Maltau J: Effect of instrumental delivery on the frequency and severity of retinal hemorrhages in the newborn. Acta Obstet Gynecol Scand 60:153, 1981 6. Haadem K, Dahlstrom JA, Lingh, et al: Anal sphincter function after delivery rupture. Obstet Gynecol 70:53, 1987 7. Helwig J, Thorp J, Bowes W: Does midline episiotomy increase the risk of third- and fourth-degree lacerations in operative vaginal deliveries? Obstet Gynecol 82:276, 1993 8. Hoult I, MacLennan A, Carrie L: Lumbar epidural analgesia in labor: Relation to fetal malposition and instrumental delivery. BMJ 1:14, 1977 9. Pearse W: Electronic recording of forcep deliveries. Am J Obstet Gynecol 86:43, 1963 10. Ramin S, Little B, Gilstap L: Survey of forceps deliveries in North America in 1990. Obstet Gynecol 81:307, 1993 11. Saunders N, Spiby H, Gilbert L, et al: Oxytocin infusion during second stage of labor in primiparous women using epidural analgesia: A randomized double blind placebo controlled group. BMJ 299:1423, 1989 12. Shaver D, Eada H, Korones S: Early and late intraventricular hemorrhage: The role of obstetric factors. Obstet Gynecol 80:831, 1992 13. Sultan A, Kamm M, Hudson C, et al: Anal-sphincter disruption during vaginal delivery. N Engl J Med 329:1905, 1993 14. Walker M, Farine D, Rolbin S, et al: Epidural anesthesia, episiotomy and obstetric laceration. Obstet Gynecol 77:668, 1991
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