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The Clinical Management of Dystocia
The Clinical Management of Dystocia PAUL O. KLINGENSMITH, M.D.*
DYSTOCIA is a broad term used to denote difficulty arising from the mechemical forces of labor. Because labor is a complex phenomenon with a fine gradient from the normal to an abnormal mechanism, arbitrary limits have been set to aid in the recognition of dystocia. Labor has been called difficult when it is prolonged or when progress is arrested. Such definitions have clinical usefulness, but fail to pinpoint the most fundamental factor in labor, the good health of mother and baby. When their welfare is jeopardized by a fault in the mechanism of labor, dystocia should be recognized. The forces of labor fall into two general groups: the active or motivating force, and the passive or resistant force. The primary active force is supplied by the uterus, a secondary active force by the abdominal muscles. Passive or resistant forces are offered by the parturient canal and fetus. These forces are closely integrated, but labor can best be understood by analysis of each force. The clinical management of dystocia deals with the recognition and treatment of their anomalies.
ANOMALIES OF THE ACTIVE FORCES OF LABOR
Prophylactic ManagenlCnt
The performance of the uterus in labor is not predictable. However, there are factors subject to antepartum influence which may condition this performance. It is known that truly refractory disturbances of uterine motility are seen most often in women in their first labor. They seem especially prone to occur in the abnormally fearful primigravida. The best known prophylactic treatment for poor uterine motility is proper preparation of the patient for labor. The physical aspects of the preparation are much less important than the psychological, for the principal objective is the establishment of the complete confidence of the patient in her arrangements. This end is obtained by the exhibition of genuine
* Associate Professor of Obstetrics and Gynecology, University of Pennsylvania School of Medicine; Associate in Obstetrics and Gynecology, Hospital of the University of Pennsylvania and Lankenau Hospital, Philadelphia. 1579
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and sympathetic interest on the part of the physician and other attendants. Physical preparation should include attention to late pregnancy discomforts to conserve energy for labor. Overdistention of the uterus predisposes to abnormal uterine motility. The cause of the abnormal distention is established by x-ray visualization of the uterine contents. When the distention is due to an excessively large single fetus or mature twins, induction of labor may be considered. However, it has not been proved that an induced labor is of better quality than that to be expected of the spontaneous contractions which would soon be forthcoming. Labor should not be induced urness a vertex is presenting and engaged, the cervix partially effaced and dilated at least 2 cm. Overdistention from hydramnios is treated with bed rest, salt restriction and diuretics. If these measures fail, release of excess fluid is indicated, provided the fetus is mature. More attention should be given to prophylactic management of the secondary force supplied by the abdominal muscles. A difficult second stage of labor can often be best resolved by good abdominal force. A well conducted program of physical training of the abdominal muscles and diaphragm may prevent dystocia in midpelvis. Managelllent in Labor
The vagaries of uterine action call for accurate diagnosis rather than hasty action. It should be recalled that the uterus contracts throughout pregnancy, and the transition into true labor may be difficult to discern. Cesarean sections have been done on patients in false labor. Regardless of the apparent force of the uterine contractions, when there is no effacement or dilatation of the cervix, the problem is one of false labor. Once progress is arrested after change in the cervix occurs, the diagnosis of abnormal uterine action should be entertained. However, lack of progress is only presumptive evidence of inefficient uterine force and should not be used as a basis for active treatment. The following case illustrates this point. CASE HISTORY. C. R., bipara, gravida III, age 32, had 2 past pregnancies and deliveries said to be normal, though no records were available. The onset of labor was normal, with left occipital transverse vertex presentation at station minus 2. The pelvic capacity was classed as ample, and no soft tissue defects were observed. Three hours after onset the membranes ruptured spontaneously; the cervix was 50 per cent effaced and 3 cm. dilated. Contractions occurred every 3 to 4 minutes and were of 30 seconds' duration; the fundus was indentable. After 6 hours there was no change in station or the cervix. The patient was rested with Demerol, 100 mg., and was regarded as a problem of poor uterine action. After a rest period and no further progress intravenous administration of 1000 cc. of 5 per cent glucose in water containing 1 cc. of pitocin was begun at 15 drops a minute. An experienced observer closely followed the contractions. Within an hour the head descended to the pelvic fioor, and delivery occurred
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spontaneously without evident trauma. However, continuous bleeding followed delivery of the infant and was not controlled_by expulsion of the placenta and firm fundal contraction. Vaginal exploration revealed a complete laceration of the cervix extending into the right broad ligament. Rapid blood replacement was begun, and total hysterectomy was carried out. The patient made a good recovery. Inspection of the specimen showed that the laceration had occurred in the area of an old cervical scar.
This patient's experience shows,that active treatment of poor uterine motility must not be based on lack of progress alone. The forces of resistance must be evaluated again, and the diagnosis of abnormal uterine action supported by direct observation of the character of the contractions. Even without special instruments such as the Lorand tocograph or the Reynolds tocodynamometer, most anomalies of motility can be detected by palpation of the uterus and cervix. The two common types of contractile dystocia are the hypotonic and the hypertonic. The characteristics of the uterine contractions seen in each type are shown in Figure 358. Hypotonic contractions are characterized by low tone and low waves
Norma.l
H~potonic
H~pertonic
Fig. 358. Diagrammatic representation of tocographic picture of normal, hypotonic and hypertonic uterine motility.
of short duration. There is failure of increasing frequency of contractions. The fundus of the uterus may be indented easily at the height of a contraction, and the cervix does not change tone. In contrast, hypertonic contractions exhibit sustained high tone. They appear hard, and the fundus is not readily indented. Careful observation will show that the lower uterine segment is contracting with force equal to or greater than that of the fundus. The lack of effacement and dilatation of the cervix in the face of hard contractions furnishes the main clue to the diagnosis of hypertonic contractile dystocia. As shown by Reynolds,1 the defect is loss of gradient of contraction from fundus to cervix with abnormal contractility of the lower uterine segment. Hypotonic Uterine Action. Hypotonic uterine action is the most frequent anomaly of the primary active force. It has fittingly been called "slow labor." The main virtue of early recognition is the helpful effect on the obstetrician. He can gear himself to the process, recalling what Robert Gooch said a century ago: "My remedy is tincture of time, the loss of which is the only thing to be regretted, for it at least produces no additional evils." Thus prepared, and having warned the patient and her family to avoid undue pressure, the physician is left calm to reflect that
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only the threat of exhaustion, infection or fetal distress will force his hand. Exhaustion may be averted by moral support, rest, fluid and calories. Rest is secured by the use of a narcotic such as Demerol, 75 to 100 mg. intramuscularly. It may be repeated in doses of 50 to 75 mg. every two to four hours. A mild hypnotic such as Seconal, 0.2 mg., may help the anxious patient, but large doses of barbiturates or other excitant drugs should be avoided. Fluids and calories are supplied by the intravenous use of 5 per cent glucose in water, approximately 500 cc. every six hours. When the fluid loss is great, as it may be in hot weather, more solution and small amounts of salt are needed. Sips of water will comfort the patient, but the stomach should not be overloaded for fear of hazardous regurgitation and aspiration. In labor prolonged by hypotonic uterine action, infection is the principal hazard to mother and infant. The potential of infection exists in all patients with ruptured membranes, and it may occur without obvious evidence of amniotic fluid leak. When labor does not become actively progressive within four hours of membrane rupture, or is prolonged beyond twelve hours with apparently intact membranes, antibiotics are indicated. The intramuscular injection of a combination of aqueous penicillin, 100,000 units, and procaine penicillin, 300,000 units, every twelve hours is good prophylactic treatment. If penicillin sensitivity or infection from penicillin-resistant organisms is suspected, intravenous Terramycin, 250 mg. every eight hours, may be used. Dosage is increased when signs of infection are present. More active treatment of hypotonic uterine action should be considered when there is no response to a good basic regimen after six to twelve hours. Artificial puncture of the membranes in indicated, provided the vertex is engaged and the cervix soft, one third dilated and half effaced. Lack of progress in labor after the membranes have been ruptured three to four hours raises a consideration of direct uterine stimulation. Various methods have been proposed to stimulate uterine action, but none has a consistent effect except the oxytocic fraction of posterior pituitary extract. The powerful action of this agent has great potential for harm, and it should never be used for expediency alone. The crux of the matter is whether the risk of infection, exhaustion or a traumatic delivery is greater than the risk of use of pituitrin. When there is doubt, it should not be used. Even when the indication seems clear, the contraindications should be reviewed carefully. A working list of regulations should include the following: 1. True labor, not progressive 2. Normal forces of resistance a. Adequate pelvis confirmed by roentgenogram
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4. 5. 6.
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b. Flexed vertex presentation c. Cervix free of scar Normal uterine muscle a. Absence of previous operative incisions b. Absence of uterine tumors c. Parity not in excess of IV d. Age under 35 years Condition of fetus good (or dead) a. Regular fetal heart sounds b. No meconium-stained liquor amnii Constant attendance by an experienced observer A rested patient.
The best physiologic effect is obtained by intravenous administration of pitocin. The concentration must not exceed 1 cc. of pitocin to 1000 cc. of 5 per cent glucose in water. Half this strength is preferable. The intravenous drip is begun at 10 to 15 drops per minute. The uterus is observed for tetany, and the fetal heart sounds are checked through successive contractions. When no adverse signs develop, the drip may be regulated to produce moderate contractions of two to three minute frequency. Should excessively strong contractions or slowing of the fetal heart sounds ensue, the drip must be slowed or cut off. If labor is normally progressive, the pitocin should be continued throughout delivery and for about thirty minutes after expulsion of the placenta to insure against relaxation bleeding. Occasionally, especially in multiparae, poor uterine motility develops after good labor has been established. This should be viewed as a probable exhaustion phenomenon. If no mechanical obstruction can be demonstrated by careful recheck, the patient should be rested and given fluids with glucose. Pitocin should not be used for fear of uterine rupture. It is safer to nurse the patient along until full dilatation permits forceps extraction. Hypertonic Uterine Action. Hypertonic uterine motility is not frequent, but it sorely tests the resources of patient and physician. Pain is severe even in the early course of labor. Drugs which disorient the patient and lead to exhausting restlessness should be avoided. A preliminary dose of Seconal or Nembutal, 0.2 mg., to allay anxiousness, and Demerol, 100 mg., or morphine, 10 to 15 mg., is preferred. Narcotics should be repeated according to the reaction of the patient, not a time schedule. Exquisite attention is needed to all details of moral and physical support and the prevention of infection. When hypertonicity persists after several doses of a narcotic, regional anesthesia should be considered. Normal patterns of contractions may develop after local nervous system suppression from caudal or spinal anesthesia. Caudal block is preferred because of better control and longer action. Artificial rupture of the membranes rarely improves hypertonic uterine action. The chance of beneficial effect must be weighed against
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the disadvantage of potential infection. It is worth trying if other measures have failed and the cervix is dilated at least 4 cm. Reynolds 2 has shown that occasionally pitocin may change incoordinate action to a normal pattern. However, tetany with fetal distress is a real threat in pitocin stimulation of the hypertonic uterus. The drug is warranted only as a last resort, and expert supervision is required. Only dilute solutions such as 0.2 to 0.4 cc. per 1000 cc. of 5 per cent glucose in water should be used. In the presence of fetal distress, maternal exhaustion or infection, the condition of the cervix determines the mode of delivery. Cesarean section is indicated unless the cervix is near full dilatation. Manual dilatation of the cervix should not be attempted, but cervical incisions with forceps extraction may be successful if the vertex is well below the spines and the cervix near full dilatation and effacement. ANOMALIES OF THE PASSIVE FORCES OF LABOR THE PASSAGEWAY
Prophylactic Manage:ment
Bony pelvic contraction is the second most common cause of dystocia. No patient should be permitted to go into labor without certain knowledge of the pelvic capacity. Certain principles warrant emphasis. 1. Detection is the essence of management. 2. Manual methods of examination cannot be depended upon for accurate diagnosis. 3. X-ray pelvimetry is indicated for all patients with suspected cephalopelvic disproportion. 4. Pelvic capacity influences but does not determine the outcome of labor. 5. A trial of labor is essential to management. Manage:ment in Labor
Pelvic Inlet Dystocia. Apparent dystocia from contraction of the pelvic inlet should be tested by labor. The object of a trial of labor is to determine whether the vertex can enter the inlet without undue risk to mother or infant. The principal focus of attention is the safety of the participants, and other events are integrated accordingly. Time per se is of little consequence, for one patient may have had an adequate trial in six hours, and . another an insufficient trial in twenty-four hours. The emotional and physical reserves of the patient need assessment. Energy should not be wasted on trivialities, but conserved for labor by moral support, rest and adequate fluid and glucose. Rupture of the membranes calls for the early use of antibiotics as described previously. Meticulous attention is
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given to the technique of all examinations; vaginal or rectal exam.imi.tions should be held to the minimum necessary for good conduct of labor. _Inlet contraction is surmounted when the vertex becomes truly engaged. This event is successful only when the mother and baby remain in good condition. The trial may fail for any of the following reasons: (1) lack of engagement of the vertex, (2) fetal distress, (3) maternal exhaustion, (4) real or threatened intrauterine infection, (5) threatened uterine rupture. Cesarean section is indicated for maternal hazard or fetal distress, whether or not the failure of engagement has been tested fully. When the participants are in good condition, no decision should be attempted until the cervix is fully dilated. Prompt cesarean section is done after one hour of dilatation with failure of engagement. Descent of caput and molding may simulate true engagement of the vertex. This error in diagnosis may lead to uterine rupture or an ill advised trial of forceps. It can be avoided by careful abdominal palpation of the vertex. In doubtful cases a lateral roentgenogram may settle the decision. M idpelvic' Plane Dystocia. The recent studies of Kaltreider3·· confirm a long-held feeling that only a trial of labor can determine midpelvic plane dystocia. In principle, the management is similar to that described for evaluation of the pelvic inlet. The practical differences are that the process is more advanced, and vaginal assistance possible. The best chance for a successful result with midpelvic contraction comes from maximum utilization of the active forces. Every effort is made to brrng the mother into second stage in good condition. Analgesia should be timed to avoid the feeling of haste created by undue pain on the part of the patient. Regional anesthesia that may detract from useful active force is avoided. The force of the abdominal muscles is _enhanced by coaching the patient. As long as the forces remain active and no maternal or fetal hazard is apparent, time should not limit the trial. Intervention is not needed until forces begin to fail or hazard is recognized. Midforceps assistance is indicated when the cervix is out of the way and the vertex truly engaged in midpelvis. If these two conditions are not met, cesarean section should be carried out directly. Midforceps extraction in a contracted pelvis is a formidable procedure. The study of Caldwell and his group4 made clear the benefit of careful analysis of the available space. When the sacrum is displaced anteriorly, but the transverse space is not crow.ded, the vertex will be found in a transverse posItion. Traction is applied to the head in this position, and anterior rotation avoided until the outlet is reached. This maneuver may be facilitated with the Barton forceps, but can be carried out with any forceps to which the operator is accustomed. When the pelvis exhibits side wall funnelling and some anterior sacral displacement, an oblique diameter offers the most available space. The space can be utilized best
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by bringing the occiput anterior, for in this position the widest head diameter is anterior to the narrowest transverse diameter of the pelvis. Extraction of the head as a persistent occipitoposterior is attempted only in the pelvis with a wide posterior segment and a narrow anterior arch. If the best space is utilized and intermittent traction of moderate degree does not bring descent, the forceps should be removed and the patient prepared promptly for cesarean section. Bony Outlet Dystocia. This is a nonexistent entity, for the posterior aspect of the outlet is soft tissue. What has been termed outlet dystocia is a problem of low midpelvic plane contraction. A narrow pubic arch associated with a heavy pelvic floor may offer unusual resistance at the outlet, but a well placed episiotomy will overcome this difficulty. Cervical Dystocia. Incoordinate uterine action is the common cause of failure of cervical dilatation, but true cervical dystocia does occur. The term should be reserved for abnormal resistance inherent in the cervix such as may result from excessive fibrosis following childbirth lacerations or operative procedures for chronic endocervicitis. When progress is arrested in spite of good uterine action and no evidence of cephalopelvic disproportion, the cervix should be palpated vaginally. The finding of a hard ring of tissue within the cervical canal confirms the suspicion of abnormal local resistance in the cervix. Manual or instrumental dilatation is avoided. Pitocin stimulation of the uterus is contraindicated for fear of producing a serious laceration, as reported earlier in this paper. When the natural powers do not effect cervical dilatation, cesarean section is indicated. Occasionally the cervix is found to be paper thin with a mere dimple at the site of the canal, a condition called conglutination of the external os. Finger or instrumental stretching of the external os results in rapid dilatation and good progress to delivery. Uterine or Ovarian Tumors. Labor may be obstructed by uterine or ovarian tumors, especially if they become lodged in the cul-de-sac ahead of the presenting part. The presence of an ovarian tumor calls for elective laparotomy with cesarean section and adnexal surgery. Elective cesarean section for apparent obstruction of the inlet from fibromyoma uteri is indicated rarely. The developments of labor should be awaited, for the tumor may be pulled upward by retraction of the lower uterine segment to permit the vertex to enter the pelvic inlet. THE PASSENGER
Prophylactic Management
The fetus offers resistance in proportion to its size and position. The fetal causes of dystocia are (1) excessive size, (2) malformation, (3) transverse lie (often called transverse presentation), (4) deflexion attitudes of the vertex, (5) breech.
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Potential fetal dystocia should be detected in advance of labor. When the abdomen is excessively large, or a well flexed vertex presentation not clearly palpable, x-ray visualization of the fetus and maternal pelvis is required. Active treatment may be indicated in advance of labor. This aspect will be considered under Management in Labor in order to maintain continuity of discussion of each particular cause of fetal dystocia. ManageDlent in Labor
Excessive Fetal Size. Excessive size of the fetus predisposes'to dystocia because of overdistention of the uterus, lack of molding of the vertex and greater bulk of the shoulder girdle. A relatively greater pelvic capacity is required for safe passageway of an infant in excess of 4000 gm. Induction of labor in advance of term is indicated rarely, and elective cesarean section considered only when gross disproportion is evident. The trial of labor should be conducted according to the principles noted previously. Every effort is directed toward getting maximum use from the natural forces. Stimulation of uterine action is contraindicated because of the possibility of unrecognized obstruction and rupture of the uterus. Fetal Malformatio"!'s. The most common malformation that may give dystocia is hydrocephalus. With vertex presentation the diagnosis depends upon palpation of an unusually broad head high in the abdomen. Confirmation should be sought by x-ray visualization. The diagnosis of hydrocephalus in breech presentation is most difficult, and x-ray views may be misleading. Unless special x-ray cephalometry technique adapted to breech presentation is used, the x-ray diagnosis of hydrocephalus should be questioned. Even then, treatment should await developments of labor. In obstruction from the after-coming hydrocephalic head, vaginal manipulations must be carried out with gentleness to avoid rupture of the overdistended lower uterine segment. Decompression is effected most readily by perforation behind the ear or at the base of the skull, utilizing long scissors or uterine dressing forceps. An obstructed hydrocephalic vertex is perforated through an accessible suture line or fontanel. Transverse Lie. The persistence of a transverse lie calls for analysis of the possible etiology before the onset of labor. About one of every four transverse lies is due to placenta previa. Complete fundal polarity of the placenta, contracted pelvis and relaxed abdominal musculatu~e are other common O'auses. The placental site and the maternal pelvis should be visualized by suitable x-ray techniques. When placenta previa or contracted pelvis is associated with transverse lie, elective cesarean section is indicated. If the pelvis is ample and the placenta normally implanted, external version may be tried. This succeeds rarely, and then the choice lies between elective section and the chance that early labor may bring the fetus around to a more favorable position. In the absence of extenuat-
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ing circumstances such as elderly primigravidity or long-time sterility, the effect of early labor should be awaited. The patient is hospitalized at the earliest sign of labor, and if well established contractions fail to correct the lie, cesarean section is indicated in fetal interest. Occasionally the diagnosis of transverse lie is not made until obstruction has developed or prolapse of an arm or cord has occurred. In any such circumstance the selection of treatment depends upon the viability of the baby, the state of the cervix and the pelvic capacity. With a live infant, cesarean section is indicated unless a dilated cervix and optimum fetopelvic proportion permit an easy version and extraction. When the baby is dead, it is possible generally to carry along until the cervix will allow extraction per vaginam. Deflexion Attitudes of the Vertex. These are seen most often with occipitoposterior positions. It is doubtful whether they are a cause of dystocia per se, although labor may be of inferior quality because of poor apposition of the presenting part against the cervix. True difficulty arises from a lack of active force of pelvic contraction and should be dealt with accordingly as described previously. Deflexion to face presentation requires careful survey of pelvic capacity and infant size. Associated pelvic contraction is an indication for cesarean section. More commonly the pelvis is ample, and the developments of labor should be awaited. When the cervix reaches half dilatation, the Thorn maneuver of conversion to a vertex deserves consideration. There is little chance for success if the face has become deeply engaged or insufficient attention has been given to the details of the procedure. The patient should be prepared as for delivery, and anesthesia secured to the point of uterine relaxation. Slight Trendelenburg tilting of the table may help in displacing the face from the pelvic inlet. When the face can be displaced, conversion to the vertex by combined abdominal and vaginal finger tip manipulation is not difficult. Then the vertex is brought into the inlet by fundal and suprapubic pressure which is maintained until uterine contractions return. Thereafter the patient is managed as for the normal vertex. Midpelvic arrest of the face with the chin anterior is due to failure of the active force or unrecognized obstruction. Uterine stimulation is avoided. If the cervix is dilated, a trial of forceps is indicated. In deep arrest with the chin posterior, anterior rotation of the chin should be attempted. If the rotation or subsequent extraction does not go easily, effort from below should be abandoned and cesarean section carried out. The management of brow presentations follows the same general principles as described for those of the face. Breech Presentations. In breech presentations, dystocia may occur with premature as well as mature infants. In the premature the relatively larger after-coming head may be trapped by a poorly dilated lower uterine segment. This may be prevented by avoiding breech extraction until
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the body has passed through the cervix. When the head is trapped, the cervix may be incised, or relaxed by general anesthesia. With a mature breech, dystocia is due to inherent disproportion or extension of the arms. When external version fails, the pelvic capacity should be surveyed by roentgenogram in advance -of labor. True pelvic contraction or borderline contraction with an excessively large baby is a sound indication for cesarean section. In labor there is no substitute for well conserved active forces, and extractions should be undertaken only on definite indications. When an extraction is necessary, complete uterine relaxation from anesthesia is prerequisite to a successful outcome. Extension of the arms will occur rarely if traction is applied slowly with the normal breech mechanism in mind. When resistance is met at the shoulder girdle, the baby should be pushed up and rotated before traction is resumed. Persistent arrest of the shoulders may require manual reduction of an arm. Arrest of the after-coming head is dealt with by forceps. SUMMARY
Dystocia is a mechanical fault of labor which jeopardizes the welfare of mother or'infant. It is understood best by analysis of each particular force of labor. Anomalies of the active force are the most frequent cause of difficult labor. Their etiology is poorly defined, but adequate preparation of the patient for labor constitutes the best known prophylactic treatment. Management in labor is based on recognition of the type of abnormality of uterine motility presented and its relationship to the other forces involved. Active treatment is founded on the principle of conservation of the natural powers, but maternal or fetal distress may require intervention. The prophylactic management of abnormal force of resistance due to the parturient canal or fetus is based on recognition of disproportion in advance of labor. However, a trial of labor is needed in most cases to determine the outcome. Neat judgment is required to evaluate progress in labor in the light of maternal and fetal safety. An obstetrician must recognize when accomplishment ceases and endurance begins. His natural bent to intervene should be guided by the principle: First do no harm. REFERENCES 1. Reynolds, S. R. M.: Physiology of the Uterus. 2d ed. New York, Paul B. Hoeber' Inc., 1949. 2. Reynolds, S. R. M.: Physiological Bases of Gynecology and Obstetrics. American Lecture Series, Monograph 128. Springfield, Ill., Charles C Thomas, 1952. 3. Kaltreider, D. F.: Criteria of Midplane Contraction. Am. J. Obst. & Gynec., 63: 392, 1952. 4. Caldwell, W. E., Moloy, H. C., and D'Esopo, D. A.: Studies on Pelvic Arrests. Am. J. Obst. & Gynec., ·36: 928, 1938. 133 South 36th Street Philadelphia 4, Pa.
DYSTOCIA is a broad term used to denote difficulty arising from the mechemical forces of labor. Because labor is a complex phenomenon with a fine gradient from the normal to an abnormal mechanism, arbitrary limits have been set to aid in the recognition of dystocia. Labor has been called difficult when it is prolonged or when progress is arrested. Such definitions have clinical usefulness, but fail to pinpoint the most fundamental factor in labor, the good health of mother and baby. When their welfare is jeopardized by a fault in the mechanism of labor, dystocia should be recognized. The forces of labor fall into two general groups: the active or motivating force, and the passive or resistant force. The primary active force is supplied by the uterus, a secondary active force by the abdominal muscles. Passive or resistant forces are offered by the parturient canal and fetus. These forces are closely integrated, but labor can best be understood by analysis of each force. The clinical management of dystocia deals with the recognition and treatment of their anomalies.
ANOMALIES OF THE ACTIVE FORCES OF LABOR
Prophylactic ManagenlCnt
The performance of the uterus in labor is not predictable. However, there are factors subject to antepartum influence which may condition this performance. It is known that truly refractory disturbances of uterine motility are seen most often in women in their first labor. They seem especially prone to occur in the abnormally fearful primigravida. The best known prophylactic treatment for poor uterine motility is proper preparation of the patient for labor. The physical aspects of the preparation are much less important than the psychological, for the principal objective is the establishment of the complete confidence of the patient in her arrangements. This end is obtained by the exhibition of genuine
* Associate Professor of Obstetrics and Gynecology, University of Pennsylvania School of Medicine; Associate in Obstetrics and Gynecology, Hospital of the University of Pennsylvania and Lankenau Hospital, Philadelphia. 1579
r 1580
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and sympathetic interest on the part of the physician and other attendants. Physical preparation should include attention to late pregnancy discomforts to conserve energy for labor. Overdistention of the uterus predisposes to abnormal uterine motility. The cause of the abnormal distention is established by x-ray visualization of the uterine contents. When the distention is due to an excessively large single fetus or mature twins, induction of labor may be considered. However, it has not been proved that an induced labor is of better quality than that to be expected of the spontaneous contractions which would soon be forthcoming. Labor should not be induced urness a vertex is presenting and engaged, the cervix partially effaced and dilated at least 2 cm. Overdistention from hydramnios is treated with bed rest, salt restriction and diuretics. If these measures fail, release of excess fluid is indicated, provided the fetus is mature. More attention should be given to prophylactic management of the secondary force supplied by the abdominal muscles. A difficult second stage of labor can often be best resolved by good abdominal force. A well conducted program of physical training of the abdominal muscles and diaphragm may prevent dystocia in midpelvis. Managelllent in Labor
The vagaries of uterine action call for accurate diagnosis rather than hasty action. It should be recalled that the uterus contracts throughout pregnancy, and the transition into true labor may be difficult to discern. Cesarean sections have been done on patients in false labor. Regardless of the apparent force of the uterine contractions, when there is no effacement or dilatation of the cervix, the problem is one of false labor. Once progress is arrested after change in the cervix occurs, the diagnosis of abnormal uterine action should be entertained. However, lack of progress is only presumptive evidence of inefficient uterine force and should not be used as a basis for active treatment. The following case illustrates this point. CASE HISTORY. C. R., bipara, gravida III, age 32, had 2 past pregnancies and deliveries said to be normal, though no records were available. The onset of labor was normal, with left occipital transverse vertex presentation at station minus 2. The pelvic capacity was classed as ample, and no soft tissue defects were observed. Three hours after onset the membranes ruptured spontaneously; the cervix was 50 per cent effaced and 3 cm. dilated. Contractions occurred every 3 to 4 minutes and were of 30 seconds' duration; the fundus was indentable. After 6 hours there was no change in station or the cervix. The patient was rested with Demerol, 100 mg., and was regarded as a problem of poor uterine action. After a rest period and no further progress intravenous administration of 1000 cc. of 5 per cent glucose in water containing 1 cc. of pitocin was begun at 15 drops a minute. An experienced observer closely followed the contractions. Within an hour the head descended to the pelvic fioor, and delivery occurred
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spontaneously without evident trauma. However, continuous bleeding followed delivery of the infant and was not controlled_by expulsion of the placenta and firm fundal contraction. Vaginal exploration revealed a complete laceration of the cervix extending into the right broad ligament. Rapid blood replacement was begun, and total hysterectomy was carried out. The patient made a good recovery. Inspection of the specimen showed that the laceration had occurred in the area of an old cervical scar.
This patient's experience shows,that active treatment of poor uterine motility must not be based on lack of progress alone. The forces of resistance must be evaluated again, and the diagnosis of abnormal uterine action supported by direct observation of the character of the contractions. Even without special instruments such as the Lorand tocograph or the Reynolds tocodynamometer, most anomalies of motility can be detected by palpation of the uterus and cervix. The two common types of contractile dystocia are the hypotonic and the hypertonic. The characteristics of the uterine contractions seen in each type are shown in Figure 358. Hypotonic contractions are characterized by low tone and low waves
Norma.l
H~potonic
H~pertonic
Fig. 358. Diagrammatic representation of tocographic picture of normal, hypotonic and hypertonic uterine motility.
of short duration. There is failure of increasing frequency of contractions. The fundus of the uterus may be indented easily at the height of a contraction, and the cervix does not change tone. In contrast, hypertonic contractions exhibit sustained high tone. They appear hard, and the fundus is not readily indented. Careful observation will show that the lower uterine segment is contracting with force equal to or greater than that of the fundus. The lack of effacement and dilatation of the cervix in the face of hard contractions furnishes the main clue to the diagnosis of hypertonic contractile dystocia. As shown by Reynolds,1 the defect is loss of gradient of contraction from fundus to cervix with abnormal contractility of the lower uterine segment. Hypotonic Uterine Action. Hypotonic uterine action is the most frequent anomaly of the primary active force. It has fittingly been called "slow labor." The main virtue of early recognition is the helpful effect on the obstetrician. He can gear himself to the process, recalling what Robert Gooch said a century ago: "My remedy is tincture of time, the loss of which is the only thing to be regretted, for it at least produces no additional evils." Thus prepared, and having warned the patient and her family to avoid undue pressure, the physician is left calm to reflect that
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only the threat of exhaustion, infection or fetal distress will force his hand. Exhaustion may be averted by moral support, rest, fluid and calories. Rest is secured by the use of a narcotic such as Demerol, 75 to 100 mg. intramuscularly. It may be repeated in doses of 50 to 75 mg. every two to four hours. A mild hypnotic such as Seconal, 0.2 mg., may help the anxious patient, but large doses of barbiturates or other excitant drugs should be avoided. Fluids and calories are supplied by the intravenous use of 5 per cent glucose in water, approximately 500 cc. every six hours. When the fluid loss is great, as it may be in hot weather, more solution and small amounts of salt are needed. Sips of water will comfort the patient, but the stomach should not be overloaded for fear of hazardous regurgitation and aspiration. In labor prolonged by hypotonic uterine action, infection is the principal hazard to mother and infant. The potential of infection exists in all patients with ruptured membranes, and it may occur without obvious evidence of amniotic fluid leak. When labor does not become actively progressive within four hours of membrane rupture, or is prolonged beyond twelve hours with apparently intact membranes, antibiotics are indicated. The intramuscular injection of a combination of aqueous penicillin, 100,000 units, and procaine penicillin, 300,000 units, every twelve hours is good prophylactic treatment. If penicillin sensitivity or infection from penicillin-resistant organisms is suspected, intravenous Terramycin, 250 mg. every eight hours, may be used. Dosage is increased when signs of infection are present. More active treatment of hypotonic uterine action should be considered when there is no response to a good basic regimen after six to twelve hours. Artificial puncture of the membranes in indicated, provided the vertex is engaged and the cervix soft, one third dilated and half effaced. Lack of progress in labor after the membranes have been ruptured three to four hours raises a consideration of direct uterine stimulation. Various methods have been proposed to stimulate uterine action, but none has a consistent effect except the oxytocic fraction of posterior pituitary extract. The powerful action of this agent has great potential for harm, and it should never be used for expediency alone. The crux of the matter is whether the risk of infection, exhaustion or a traumatic delivery is greater than the risk of use of pituitrin. When there is doubt, it should not be used. Even when the indication seems clear, the contraindications should be reviewed carefully. A working list of regulations should include the following: 1. True labor, not progressive 2. Normal forces of resistance a. Adequate pelvis confirmed by roentgenogram
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4. 5. 6.
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b. Flexed vertex presentation c. Cervix free of scar Normal uterine muscle a. Absence of previous operative incisions b. Absence of uterine tumors c. Parity not in excess of IV d. Age under 35 years Condition of fetus good (or dead) a. Regular fetal heart sounds b. No meconium-stained liquor amnii Constant attendance by an experienced observer A rested patient.
The best physiologic effect is obtained by intravenous administration of pitocin. The concentration must not exceed 1 cc. of pitocin to 1000 cc. of 5 per cent glucose in water. Half this strength is preferable. The intravenous drip is begun at 10 to 15 drops per minute. The uterus is observed for tetany, and the fetal heart sounds are checked through successive contractions. When no adverse signs develop, the drip may be regulated to produce moderate contractions of two to three minute frequency. Should excessively strong contractions or slowing of the fetal heart sounds ensue, the drip must be slowed or cut off. If labor is normally progressive, the pitocin should be continued throughout delivery and for about thirty minutes after expulsion of the placenta to insure against relaxation bleeding. Occasionally, especially in multiparae, poor uterine motility develops after good labor has been established. This should be viewed as a probable exhaustion phenomenon. If no mechanical obstruction can be demonstrated by careful recheck, the patient should be rested and given fluids with glucose. Pitocin should not be used for fear of uterine rupture. It is safer to nurse the patient along until full dilatation permits forceps extraction. Hypertonic Uterine Action. Hypertonic uterine motility is not frequent, but it sorely tests the resources of patient and physician. Pain is severe even in the early course of labor. Drugs which disorient the patient and lead to exhausting restlessness should be avoided. A preliminary dose of Seconal or Nembutal, 0.2 mg., to allay anxiousness, and Demerol, 100 mg., or morphine, 10 to 15 mg., is preferred. Narcotics should be repeated according to the reaction of the patient, not a time schedule. Exquisite attention is needed to all details of moral and physical support and the prevention of infection. When hypertonicity persists after several doses of a narcotic, regional anesthesia should be considered. Normal patterns of contractions may develop after local nervous system suppression from caudal or spinal anesthesia. Caudal block is preferred because of better control and longer action. Artificial rupture of the membranes rarely improves hypertonic uterine action. The chance of beneficial effect must be weighed against
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the disadvantage of potential infection. It is worth trying if other measures have failed and the cervix is dilated at least 4 cm. Reynolds 2 has shown that occasionally pitocin may change incoordinate action to a normal pattern. However, tetany with fetal distress is a real threat in pitocin stimulation of the hypertonic uterus. The drug is warranted only as a last resort, and expert supervision is required. Only dilute solutions such as 0.2 to 0.4 cc. per 1000 cc. of 5 per cent glucose in water should be used. In the presence of fetal distress, maternal exhaustion or infection, the condition of the cervix determines the mode of delivery. Cesarean section is indicated unless the cervix is near full dilatation. Manual dilatation of the cervix should not be attempted, but cervical incisions with forceps extraction may be successful if the vertex is well below the spines and the cervix near full dilatation and effacement. ANOMALIES OF THE PASSIVE FORCES OF LABOR THE PASSAGEWAY
Prophylactic Manage:ment
Bony pelvic contraction is the second most common cause of dystocia. No patient should be permitted to go into labor without certain knowledge of the pelvic capacity. Certain principles warrant emphasis. 1. Detection is the essence of management. 2. Manual methods of examination cannot be depended upon for accurate diagnosis. 3. X-ray pelvimetry is indicated for all patients with suspected cephalopelvic disproportion. 4. Pelvic capacity influences but does not determine the outcome of labor. 5. A trial of labor is essential to management. Manage:ment in Labor
Pelvic Inlet Dystocia. Apparent dystocia from contraction of the pelvic inlet should be tested by labor. The object of a trial of labor is to determine whether the vertex can enter the inlet without undue risk to mother or infant. The principal focus of attention is the safety of the participants, and other events are integrated accordingly. Time per se is of little consequence, for one patient may have had an adequate trial in six hours, and . another an insufficient trial in twenty-four hours. The emotional and physical reserves of the patient need assessment. Energy should not be wasted on trivialities, but conserved for labor by moral support, rest and adequate fluid and glucose. Rupture of the membranes calls for the early use of antibiotics as described previously. Meticulous attention is
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given to the technique of all examinations; vaginal or rectal exam.imi.tions should be held to the minimum necessary for good conduct of labor. _Inlet contraction is surmounted when the vertex becomes truly engaged. This event is successful only when the mother and baby remain in good condition. The trial may fail for any of the following reasons: (1) lack of engagement of the vertex, (2) fetal distress, (3) maternal exhaustion, (4) real or threatened intrauterine infection, (5) threatened uterine rupture. Cesarean section is indicated for maternal hazard or fetal distress, whether or not the failure of engagement has been tested fully. When the participants are in good condition, no decision should be attempted until the cervix is fully dilated. Prompt cesarean section is done after one hour of dilatation with failure of engagement. Descent of caput and molding may simulate true engagement of the vertex. This error in diagnosis may lead to uterine rupture or an ill advised trial of forceps. It can be avoided by careful abdominal palpation of the vertex. In doubtful cases a lateral roentgenogram may settle the decision. M idpelvic' Plane Dystocia. The recent studies of Kaltreider3·· confirm a long-held feeling that only a trial of labor can determine midpelvic plane dystocia. In principle, the management is similar to that described for evaluation of the pelvic inlet. The practical differences are that the process is more advanced, and vaginal assistance possible. The best chance for a successful result with midpelvic contraction comes from maximum utilization of the active forces. Every effort is made to brrng the mother into second stage in good condition. Analgesia should be timed to avoid the feeling of haste created by undue pain on the part of the patient. Regional anesthesia that may detract from useful active force is avoided. The force of the abdominal muscles is _enhanced by coaching the patient. As long as the forces remain active and no maternal or fetal hazard is apparent, time should not limit the trial. Intervention is not needed until forces begin to fail or hazard is recognized. Midforceps assistance is indicated when the cervix is out of the way and the vertex truly engaged in midpelvis. If these two conditions are not met, cesarean section should be carried out directly. Midforceps extraction in a contracted pelvis is a formidable procedure. The study of Caldwell and his group4 made clear the benefit of careful analysis of the available space. When the sacrum is displaced anteriorly, but the transverse space is not crow.ded, the vertex will be found in a transverse posItion. Traction is applied to the head in this position, and anterior rotation avoided until the outlet is reached. This maneuver may be facilitated with the Barton forceps, but can be carried out with any forceps to which the operator is accustomed. When the pelvis exhibits side wall funnelling and some anterior sacral displacement, an oblique diameter offers the most available space. The space can be utilized best
. 1586
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by bringing the occiput anterior, for in this position the widest head diameter is anterior to the narrowest transverse diameter of the pelvis. Extraction of the head as a persistent occipitoposterior is attempted only in the pelvis with a wide posterior segment and a narrow anterior arch. If the best space is utilized and intermittent traction of moderate degree does not bring descent, the forceps should be removed and the patient prepared promptly for cesarean section. Bony Outlet Dystocia. This is a nonexistent entity, for the posterior aspect of the outlet is soft tissue. What has been termed outlet dystocia is a problem of low midpelvic plane contraction. A narrow pubic arch associated with a heavy pelvic floor may offer unusual resistance at the outlet, but a well placed episiotomy will overcome this difficulty. Cervical Dystocia. Incoordinate uterine action is the common cause of failure of cervical dilatation, but true cervical dystocia does occur. The term should be reserved for abnormal resistance inherent in the cervix such as may result from excessive fibrosis following childbirth lacerations or operative procedures for chronic endocervicitis. When progress is arrested in spite of good uterine action and no evidence of cephalopelvic disproportion, the cervix should be palpated vaginally. The finding of a hard ring of tissue within the cervical canal confirms the suspicion of abnormal local resistance in the cervix. Manual or instrumental dilatation is avoided. Pitocin stimulation of the uterus is contraindicated for fear of producing a serious laceration, as reported earlier in this paper. When the natural powers do not effect cervical dilatation, cesarean section is indicated. Occasionally the cervix is found to be paper thin with a mere dimple at the site of the canal, a condition called conglutination of the external os. Finger or instrumental stretching of the external os results in rapid dilatation and good progress to delivery. Uterine or Ovarian Tumors. Labor may be obstructed by uterine or ovarian tumors, especially if they become lodged in the cul-de-sac ahead of the presenting part. The presence of an ovarian tumor calls for elective laparotomy with cesarean section and adnexal surgery. Elective cesarean section for apparent obstruction of the inlet from fibromyoma uteri is indicated rarely. The developments of labor should be awaited, for the tumor may be pulled upward by retraction of the lower uterine segment to permit the vertex to enter the pelvic inlet. THE PASSENGER
Prophylactic Management
The fetus offers resistance in proportion to its size and position. The fetal causes of dystocia are (1) excessive size, (2) malformation, (3) transverse lie (often called transverse presentation), (4) deflexion attitudes of the vertex, (5) breech.
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Potential fetal dystocia should be detected in advance of labor. When the abdomen is excessively large, or a well flexed vertex presentation not clearly palpable, x-ray visualization of the fetus and maternal pelvis is required. Active treatment may be indicated in advance of labor. This aspect will be considered under Management in Labor in order to maintain continuity of discussion of each particular cause of fetal dystocia. ManageDlent in Labor
Excessive Fetal Size. Excessive size of the fetus predisposes'to dystocia because of overdistention of the uterus, lack of molding of the vertex and greater bulk of the shoulder girdle. A relatively greater pelvic capacity is required for safe passageway of an infant in excess of 4000 gm. Induction of labor in advance of term is indicated rarely, and elective cesarean section considered only when gross disproportion is evident. The trial of labor should be conducted according to the principles noted previously. Every effort is directed toward getting maximum use from the natural forces. Stimulation of uterine action is contraindicated because of the possibility of unrecognized obstruction and rupture of the uterus. Fetal Malformatio"!'s. The most common malformation that may give dystocia is hydrocephalus. With vertex presentation the diagnosis depends upon palpation of an unusually broad head high in the abdomen. Confirmation should be sought by x-ray visualization. The diagnosis of hydrocephalus in breech presentation is most difficult, and x-ray views may be misleading. Unless special x-ray cephalometry technique adapted to breech presentation is used, the x-ray diagnosis of hydrocephalus should be questioned. Even then, treatment should await developments of labor. In obstruction from the after-coming hydrocephalic head, vaginal manipulations must be carried out with gentleness to avoid rupture of the overdistended lower uterine segment. Decompression is effected most readily by perforation behind the ear or at the base of the skull, utilizing long scissors or uterine dressing forceps. An obstructed hydrocephalic vertex is perforated through an accessible suture line or fontanel. Transverse Lie. The persistence of a transverse lie calls for analysis of the possible etiology before the onset of labor. About one of every four transverse lies is due to placenta previa. Complete fundal polarity of the placenta, contracted pelvis and relaxed abdominal musculatu~e are other common O'auses. The placental site and the maternal pelvis should be visualized by suitable x-ray techniques. When placenta previa or contracted pelvis is associated with transverse lie, elective cesarean section is indicated. If the pelvis is ample and the placenta normally implanted, external version may be tried. This succeeds rarely, and then the choice lies between elective section and the chance that early labor may bring the fetus around to a more favorable position. In the absence of extenuat-
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ing circumstances such as elderly primigravidity or long-time sterility, the effect of early labor should be awaited. The patient is hospitalized at the earliest sign of labor, and if well established contractions fail to correct the lie, cesarean section is indicated in fetal interest. Occasionally the diagnosis of transverse lie is not made until obstruction has developed or prolapse of an arm or cord has occurred. In any such circumstance the selection of treatment depends upon the viability of the baby, the state of the cervix and the pelvic capacity. With a live infant, cesarean section is indicated unless a dilated cervix and optimum fetopelvic proportion permit an easy version and extraction. When the baby is dead, it is possible generally to carry along until the cervix will allow extraction per vaginam. Deflexion Attitudes of the Vertex. These are seen most often with occipitoposterior positions. It is doubtful whether they are a cause of dystocia per se, although labor may be of inferior quality because of poor apposition of the presenting part against the cervix. True difficulty arises from a lack of active force of pelvic contraction and should be dealt with accordingly as described previously. Deflexion to face presentation requires careful survey of pelvic capacity and infant size. Associated pelvic contraction is an indication for cesarean section. More commonly the pelvis is ample, and the developments of labor should be awaited. When the cervix reaches half dilatation, the Thorn maneuver of conversion to a vertex deserves consideration. There is little chance for success if the face has become deeply engaged or insufficient attention has been given to the details of the procedure. The patient should be prepared as for delivery, and anesthesia secured to the point of uterine relaxation. Slight Trendelenburg tilting of the table may help in displacing the face from the pelvic inlet. When the face can be displaced, conversion to the vertex by combined abdominal and vaginal finger tip manipulation is not difficult. Then the vertex is brought into the inlet by fundal and suprapubic pressure which is maintained until uterine contractions return. Thereafter the patient is managed as for the normal vertex. Midpelvic arrest of the face with the chin anterior is due to failure of the active force or unrecognized obstruction. Uterine stimulation is avoided. If the cervix is dilated, a trial of forceps is indicated. In deep arrest with the chin posterior, anterior rotation of the chin should be attempted. If the rotation or subsequent extraction does not go easily, effort from below should be abandoned and cesarean section carried out. The management of brow presentations follows the same general principles as described for those of the face. Breech Presentations. In breech presentations, dystocia may occur with premature as well as mature infants. In the premature the relatively larger after-coming head may be trapped by a poorly dilated lower uterine segment. This may be prevented by avoiding breech extraction until
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the body has passed through the cervix. When the head is trapped, the cervix may be incised, or relaxed by general anesthesia. With a mature breech, dystocia is due to inherent disproportion or extension of the arms. When external version fails, the pelvic capacity should be surveyed by roentgenogram in advance -of labor. True pelvic contraction or borderline contraction with an excessively large baby is a sound indication for cesarean section. In labor there is no substitute for well conserved active forces, and extractions should be undertaken only on definite indications. When an extraction is necessary, complete uterine relaxation from anesthesia is prerequisite to a successful outcome. Extension of the arms will occur rarely if traction is applied slowly with the normal breech mechanism in mind. When resistance is met at the shoulder girdle, the baby should be pushed up and rotated before traction is resumed. Persistent arrest of the shoulders may require manual reduction of an arm. Arrest of the after-coming head is dealt with by forceps. SUMMARY
Dystocia is a mechanical fault of labor which jeopardizes the welfare of mother or'infant. It is understood best by analysis of each particular force of labor. Anomalies of the active force are the most frequent cause of difficult labor. Their etiology is poorly defined, but adequate preparation of the patient for labor constitutes the best known prophylactic treatment. Management in labor is based on recognition of the type of abnormality of uterine motility presented and its relationship to the other forces involved. Active treatment is founded on the principle of conservation of the natural powers, but maternal or fetal distress may require intervention. The prophylactic management of abnormal force of resistance due to the parturient canal or fetus is based on recognition of disproportion in advance of labor. However, a trial of labor is needed in most cases to determine the outcome. Neat judgment is required to evaluate progress in labor in the light of maternal and fetal safety. An obstetrician must recognize when accomplishment ceases and endurance begins. His natural bent to intervene should be guided by the principle: First do no harm. REFERENCES 1. Reynolds, S. R. M.: Physiology of the Uterus. 2d ed. New York, Paul B. Hoeber' Inc., 1949. 2. Reynolds, S. R. M.: Physiological Bases of Gynecology and Obstetrics. American Lecture Series, Monograph 128. Springfield, Ill., Charles C Thomas, 1952. 3. Kaltreider, D. F.: Criteria of Midplane Contraction. Am. J. Obst. & Gynec., 63: 392, 1952. 4. Caldwell, W. E., Moloy, H. C., and D'Esopo, D. A.: Studies on Pelvic Arrests. Am. J. Obst. & Gynec., ·36: 928, 1938. 133 South 36th Street Philadelphia 4, Pa.