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Shoulder Dystocia: Prevention and Management
Obstet Gynecol Clin N Am 32 (2005) 297 – 305
Shoulder Dystocia: Prevention and Management Robert B. Gherman, MD* Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, Washington Adventist Hospital, 7600 Carrou Avenue, 3rd floor, Takoma Park, MD 20912, USA
Despite its infrequent occurrence (0.2%–3% of all deliveries), all health care providers who attend vaginal deliveries must be prepared to handle this unpredictable obstetric emergency [1]. Shoulder dystocia represents the failure of delivery of the fetal shoulders, whether it be the anterior, posterior, or both fetal shoulders [2]. Shoulder dystocia results from a size discrepancy between the fetal shoulders and the pelvic inlet. A persistent anteroposterior location of the fetal shoulders at the pelvic brim occurs when there is increased resistance between the fetal skin and vaginal walls (eg, with macrosomia), with a large fetal chest relative to the biparietal diameter, and when truncal rotation does not occur (eg, precipitous labor) [3]. Shoulder dystocia also can occur from impaction of the posterior fetal shoulder on the maternal sacral promontory. Most authors have defined this obstetric emergency to include deliveries that require maneuvers in addition to gentle downward traction on the fetal head to effect delivery. Several studies have proposed defining shoulder dystocia as a prolonged head-to-body delivery interval (60 seconds) or the use of ancillary obstetric maneuvers, because this time represented the mean plus two standard deviations [4,5].
Maternal and fetal risks Postpartum hemorrhage and the unintentional extension of an episiotomy or laceration into the rectum (fourth-degree laceration) are the most common
* 21636 Ripplemead Drive, Laytonsville, MD 20882. E-mail address: [email protected] 0889-8545/05/$ – see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.ogc.2004.12.006
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maternal complications associated with shoulder dystocia. In the study by Gherman et al [6], these complications occurred in 11% and 3.8%, respectively, of the described shoulder dystocias. Other complications that have been reported have included vaginal lacerations, cervical tears, bladder atony, and uterine rupture. Maternal symphyseal separation and lateral femoral cutaneous neuropathy also have been associated with overly aggressive hyperflexion of the maternal legs [7]. Risks to the physician mainly involve litigation, because brachial plexus palsy, central neurologic dysfunction, and perinatal death account for most of the shoulder dystocia–related lawsuits. A clearly documented medical record may prove to be helpful in the medicolegal arena (Box 1) [8,9]. A large retrospective study that evaluated 285 cases of shoulder dystocia found that the fetal injury rate was 24.9%, including 48 (16.8%) brachial plexus palsies, 27 (9.5%) clavicular fractures, and 12 (4.2%) humeral fractures [10]. Unilateral brachial plexus injuries have represented the most common neurologic injury sustained by neonates. The right arm is usually affected (64.6%) because the left occiput anterior presentation leaves the right shoulder impinged against the symphysis pubis [10]. Brachial plexus injury has been found to complicate up to 21% of all cases of shoulder dystocia [11]. Most (80%) of these nerve injuries have been located within C5-C6 nerve roots (Erb-Duchenne palsy). Other types of brachial plexus injuries that have been described include Klumpke’s palsy (C8-T1), an intermediate palsy, and complete palsy of the entire brachial plexus. Diaphragmatic paralysis, Horner’s syndrome, and facial nerve injuries have been reported to occasionally accompany brachial plexus palsy [3]. Approximately one third of brachial plexus palsies are associated with
Box 1. Suggested medicolegal documentation for shoulder dystocia When and how dystocia was diagnosed Progress of labor (active phase and second stage) Position and rotation of the infant’s head Presence of episiotomy, if performed Anesthesia required Estimation of force of traction applied Order, duration, and results of maneuvers used Duration of shoulder dystocia Documentation of adequate pelvimetry before initiating labor induction or augmentation Neonatal and obstetric impressions of the infant after delivery Information given to gravida that shoulder dystocia had occurred Data from Acker DB. A shoulder dystocia intervention form. Obstet Gynecol 1991;78:150–1.
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Table 1 Common complications associated with shoulder dystocia Maternal
Accoucheur
Neonatal
Third- or fourth-degree lacerations Postpartum hemorrhage
Terror Medical liabilty
Erb’s palsy Klumpke’s palsy Clavicular fracture Humeral fracture Hypoxia Permanent brain injury Death
a concomitant bone fracture, most commonly the clavicle (94%) [8]. Neonatal radial fracture also can be associated with shoulder dystocia or the maneuvers used for the alleviation of shoulder dystocia [12]. The study by Gherman et al [10] compared shoulder dystocia cases based on the absence or presence of direct fetal manipulative maneuvers (Woods, posterior arm extraction, or Zavanelli). They found that the overall incidence of fetal bone fracture (16.5% versus 11.4%; P = 0.21) and brachial plexus palsy (21.3% versus 13.3%; P = 0.1) were not different between the two groups. Similar findings previously were been reported by Nocon et al [13], who grouped techniques used to disimpact the shoulder into major treatment categories. None of the major categories revealed a statistically significant difference when compared with respect to fetal injury. In this study, the authors found incidences of injury of 14.9%, 14.3%, 37.9%, and 20%, respectively, associated with McRoberts, rotations, posterior arm delivery, and suprapubic pressure (Table 1).
Prenatal: identifying the pregnancy at risk Research clearly has shown that there is a significantly increased risk of shoulder dystocia as birth weight increases. The percentages of births complicated by shoulder dystocia for unassisted births not complicated by diabetes were 5.2% for infants who weighed 4000 to 4250 g, 9.1% for infants 4250 to 4500 g, 14.3% for infants 4500 to 4750 g, and 21.1% for infants 4750 to 5000 g [14]. One must remember, however, that approximately 50% to 60% of cases of shoulder dystocia occur in infants who weigh less than 4000 g. Even if the birth weight of an infant is more than 4000 g, shoulder dystocia complicates only 3.3% of the deliveries [15,16]. From a prospective point of view, prepregnancy and antepartum risk factors, such as previous delivery of an infant with macrosomia, pre-existing or pregnancy-induced diabetes mellitus, multiparity, excessive maternal weight gain, and post-date gestation, have exceedingly poor predictive value for the prediction of shoulder dystocia. For example, one study found that only 32% of patients were obese (N 90 kg), 25% had excessive weight gain (N 20 kg), 8%
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had short stature (b 60 in), 6% were more than 42 weeks’ gestation, 3% were of advanced maternal age, and 2% had a personal history of diabetes mellitus [17]. In a case control study from the Northern and Central Alberta Perinatal Outreach Program, maternal obesity (defined as more than 91 kg) was not associated with shoulder dystocia when multivariable logistic regression analysis was used to control for confounding effects [18]. Ultrasonographic estimation of fetal weight, performed during either the late third trimester or the intrapartum period, has been used commonly to estimate the risk of shoulder dystocia via prediction of birth weight. To date, however, no studies have evaluated this relationship specifically in a patient population in which routine ultrasounds are performed. Late pregnancy ultrasound likewise displays low sensitivity (22%–44%), exceedingly poor positive predictive value (30%–44%), decreasing accuracy with increasing birth weight, and an overall tendency to overestimate the birth weight. For this reason, the American College of Obstetrician and Gynecologists recently noted that attempted vaginal delivery is not contraindicated for women with estimated fetal weights up to 5000 g in the absence of maternal diabetes [19,20]. Patients with insulin-requiring diabetes mellitus seem to warrant special evaluation for shoulder dystocia. The risk of shoulder dystocia for unassisted births to mothers with diabetes has been found to be 8.4%, 12.3%, 19.9%, and 23.5% when the birth weight is 4000 to 4250 g, 4250 to 4500 g, 4500 to 4750 g, or more than 4750 g, respectively [14]. Changes in fetal body configuration (eg, larger trunk and chest circumferences, increased bisacromial diameters, and chest-to-head disproportion) do not allow the fetal shoulders to rotate into the oblique diameter. In a similar fashion, patients with a history of shoulder dystocia that complicated a prior vaginal delivery merit consideration for recurrence. Recurrence risks for shoulder dystocia range between 11.9% and 16.7%. Maternal and fetal factors that have been shown to be significantly associated with recurrent shoulder dystocia include birth weight more than the index pregnancy, time in the second stage of labor, and birth weight more than 4000 g [1]. A policy of universal elective cesarean delivery has not been recommended for this cohort of patients [20]; however, antepartum counseling and discussion of recurrence risks should be undertaken with consideration of the current estimate of fetal weight, the presence of maternal glucose intolerance, and whether the prior shoulder dystocia resulted in transient or permanent neurologic injury. Practical management of shoulder dystocia Shoulder dystocia usually is heralded by the classic ‘‘turtle sign’’; after the fetal head is delivered, it retracts back tightly against the maternal perineum. Shoulder dystocia, however, typically is not diagnosed until attempts at downward traction have been unsuccessful in delivering one or both shoulders. The patient should be instructed to stop pushing after the shoulder dystocia is initially recognized. Maternal expulsive efforts, however, must be reinstituted
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after the fetal shoulders have been converted to the oblique diameter to achieve delivery. If the provider is alone, additional assistance may be provided by summoning other obstetricians, an anesthetist or anesthesiologist, additional nursing support, and a pediatrician. Umbilical cord compression, most commonly between the fetal body and maternal pelvis, leads to a decrease in the fetal pH at a rate of 0.04 U/min. If a nuchal cord is present and cannot be reduced easily over the fetal head, clamping and cutting of the cord should be avoided until the shoulder dystocia has been alleviated [21]. Most, if not all, of the commonly encountered shoulder dystocia episodes are able to be relieved within several minutes. Although research studies have been unable to predict an exact time limit at which irreversible brain injury occurs, it is reasonable to assume that the risk of permanent central neurologic dysfunction is associated with prolongation of the head/ shoulder interval thresholds. At the time of delivery, if shoulder dystocia is a concern, some clinicians have empirically advocated immediately proceeding to delivery of the fetal shoulders to maintain the forward momentum of the fetus. Others support a short delay in delivery of the shoulders, arguing that the endogenous rotational mechanics of the second stage may spontaneously alleviate the obstruction. Obstetricians also may use the McRoberts’ maneuver ‘‘prophylactically’’ to decrease the risk of shoulder dystocia or shorten the second stage of labor. A clinical trial randomized patients with estimated fetal weights more than 3800 g to undergo either prophylactic maneuvers (ie, McRoberts maneuver and suprapubic pressure) or maneuvers only after delivery of the fetal head, if shoulder dystocia was identified. This study, however, found that head-to-body delivery times, an indirect proxy for shoulder dystocia, did not differ between the prophylactic and control patients [22]. The use of the McRoberts’ maneuver before the clinical diagnosis of shoulder dystocia does not significantly change the traction forces applied to the fetal head during vaginal delivery in multiparous patients [23]. Although many maneuvers have been described for the successful alleviation of shoulder dystocia (Box 2), no randomized controlled trials or laboratory experiments have compared these techniques directly. Most obstetricians currently use the McRoberts’ maneuver as their initial step for the disimpaction of the shoulder. In a retrospective review of 236 shoulder dystocia cases that occurred between 1991 and 1994 at Los Angeles County/University of Southern California Medical Center, this maneuver alone alleviated 42% of cases. Trends toward lower rates of maternal and neonatal morbidity also were associated with the McRoberts’ maneuver [6]. The McRoberts’ maneuver, performed by sharply flexing the maternal thighs onto the abdomen, results in a straightening of the maternal sacrum relative to the lumbar spine with consequent cephalic rotation of the symphysis pubis [24]. Care should be taken to avoid prolonged or overly aggressive application of the McRoberts’ maneuver because the fibrocartilaginous articular surfaces of the symphysis pubis and surrounding ligaments may be stretched unduly.
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Box 2. Maneuvers for the alleviation of shoulder dystocia Maternal hip hyperflexion (McRoberts’ maneuver) Suprapubic pressure Rotational maneuvers Wood’s maneuver Rubin’s maneuver Delivery of the posterior arm (Barnum maneuver) ‘‘All fours’’ (Gaskin maneuver) Cephalic replacement Zavanelli Modified Zavanelli Symphysiotomy Abdominal rescue through hysterotomy
Most patients can assume the proper position for the McRoberts’ maneuver with little difficulty. Women may be instructed to grasp the posterior aspect of their thighs and pull themselves into position, with family members or health care professionals providing any assistance necessary. An obstetrician also may choose to flex both of the patient’s legs. Problems may occur when moving an obese patient or a woman who has undergone a dense epidural motor blockade. Because shoulder dystocia is considered to be a ‘‘bony dystocia,’’ episiotomy alone does not release the impacted shoulder. The need for cutting a generous episiotomy or procto-episiotomy must be based on clinical circumstances, such as a narrow vaginal fourchette in a primigravida patient. This procedure may allow the fetal rotational maneuvers to be performed with ease and create more room for attempted delivery of the posterior arm. Management by episiotomy or procto-episiotomy is associated with a nearly sevenfold increase in the rate of severe perineal trauma without benefit of reducing the occurrence of neonatal depression or brachial plexus palsy [25]. All attendants should refrain from applying fundal pressure as a maneuver for the alleviation of the shoulder dystocia. Pushing on the fundus simply duplicates a maternal directional expulsive force that already has failed to deliver the fetal shoulder and serves only to impact further the anterior shoulder behind the symphysis pubis. The use of fundal pressure also has been associated with an increased risk of Erb’s palsy and thoracic spinal cord injury in the neonate [26]. Suprapubic pressure, commonly administered by nursing personnel, is typically given immediately before or in direct conjunction with the McRoberts’ maneuver. This pressure usually is directed posteriorly in an attempt to force the anterior shoulder under the symphysis pubis. Other described techniques for suprapubic pressure have included lateral application from either side of the maternal abdomen and alternating between sides using a rocking pressure [27].
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Many cases of shoulder dystocia require the performance of several maneuvers to alleviate the impaction. Stallings et al [28] found that slightly more than one third of patients required more than two maneuvers. When more complex maneuvers are required, either fetal rotational maneuvers or posterior arm extraction may be used. In the Woods’ corkscrew maneuver, the practitioner attempts to abduct the posterior shoulder by exerting pressure onto the anterior surface of the posterior shoulder. In the Rubin’s (reverse Woods’) maneuver, pressure is applied to the posterior surface of the most accessible part of the fetal shoulder (ie, either the anterior or posterior shoulder) to effect shoulder adduction. These rotational maneuvers, however, may be difficult to perform when the anterior shoulder is tightly wedged underneath the symphysis pubis. It may be necessary to push the fetus slightly upward to facilitate the rotation. By replacing the bisacromial diameter with the axillo-acromial diameter, posterior arm delivery creates a 20% reduction in shoulder diameter [29]. To perform delivery of the posterior fetal arm, pressure should be applied by the delivering provider at the antecubital fossa to flex the fetal forearm. The arm is subsequently swept out over the infant’s chest and delivered over the perineum. Rotation of the fetal trunk to bring the posterior arm anteriorly is sometimes required. Grasping and pulling directly on the fetal arm and applying pressure onto the mid-humeral shaft should be avoided because bone fracture may occur. The previously mentioned maneuvers typically are able to be attempted within 4 to 5 minutes after identification of the shoulder dystocia. If the shoulder dystocia remains undelivered, a bilateral shoulder dystocia or posterior arm shoulder dystocia may be present. The latter is suggested by the presence of the posterior arm being maintained at the level of the pelvic inlet and an inability to perform posterior arm extraction. These intractable shoulder dystocias warrant the performance of heroic techniques, such as the Zavanelli maneuver, symphysiotomy, or hysterotomy. Performance of these maneuvers is complicated by a provider’s lack of clinical experience with these maneuvers, performance under emergent conditions, and significant maternal and neonatal complications inherent in the procedures. In the Zavanelli maneuver, the head is rotated back to a prerestitution position and then gently flexed. Constant firm pressure is used to push the head back into the vagina and cesarean delivery is subsequently performed. Halothane or other general anesthetic agents, in conjunction with tocolytic agents, may be administered in preparation for and during the Zavanelli maneuver. Oral or intravenous nitroglycerin also may be used. The modification of the original Zavanelli maneuver may be used to potentially reduce maternal morbidity. As described by Zelig and Gherman [30], maternal expulsive efforts were initiated after the obstetricians observed that the biparietal diameter had passed back through the introitius and the shoulders were felt to disimpact. This modification should be attempted only as long as no evidence of intrauterine fetal compromise exists. To perform a symphysiotomy, the patient should be placed in an exaggerated lithotomy position. Although its placement may be difficult secondary to
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obstruction, a Foley catheter can help to identify the urethra. With the physician’s index and middle finger displacing the urethra laterally, the cephalad portion of the symphysis is incised with a scalpel blade or Kelly clamp. Hysterotomy also may be performed either to resolve the shoulder dystocia primarily or assist with vaginal techniques. The posterior fetal arm may be delivered through the transverse uterine incision with subsequent passage of the hand to a vaginal assistant. The abdominal surgeon can apply pressure on the anterior fetal shoulder to allow rotation to the oblique diameter. Before performing these techniques, one may consider using the ‘‘all-fours’’ technique, in which the patient is rolled from her existing position onto her hands and knees [31]. The downward force of gravity or a favorable change in pelvic diameters produced by this maneuver may allow disimpaction of the fetal shoulder. Older textbooks have described deliberate clavicular fracture as a maneuver of last resort, performed by exerting direct upward pressure on the mid-portion of the fetal clavicle. In reality, however, this has not been reported in the recent literature because it is technically difficult to perform and risks serious injury to the underlying vascular and pulmonary structures in the fetus.
Summary Knowledge of the maneuvers used for the alleviation of shoulder dystocia is relevant not only for obstetric residents and attending house staff but also for family practitioners, nurses, and nurse midwives. The performance of shoulder dystocia ‘‘drills’’ can be helpful not only to coordinate a teamwork approach to this obstetric emergency but also provide an opportunity to practice the maneuvers. Shoulder dystocia continues to represent an immense area of clinical interest because it typically occurs without prediction. All patients in labor should be considered at risk for developing shoulder dystocia.
References [1] Gherman RB. Shoulder dystocia: an evidence-based evaluation of the obstetric nightmare. Clin Obstet Gynecol 2002;45:345 – 62. [2] Collins JH, Collins CL. What is shoulder dystocia? J Reprod Med 2001;46:148 – 9. [3] Gherman RB, Ouzounian JG, Goodwin TM. Brachial plexus palsy: an in utero injury? Am J Obstet Gynecol 1999;180:1303 – 7. [4] Spong CY, Beall M, Rodrigues D, et al. An objective definition of shoulder dystocia: prolonged head-to-body delivery intervals and/or the use of ancillary obstetric maneuvers. Obstet Gynecol 1995;86:433 – 6. [5] Beall MH, Spong C, McKay J, et al. Objective definition of shoulder dystocia: a prospective evaluation. Am J Obstet Gynecol 1998;179:934 – 7. [6] Gherman RB, Goodwin TM, Souter I, et al. The McRoberts’ maneuver for the alleviation of shoulder dystocia: how successful is it? Am J Obstet Gynecol 1997;176:656 – 61. [7] Gherman RB, Ouzounian JG, Incerpi MH, et al. Symphyseal separation and transient femo-
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[8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22]
[23]
[24] [25]
[26] [27] [28] [29] [30] [31]
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ral neuropathy associated with the McRoberts’ maneuver. Am J Obstet Gynecol 1998;178: 609 – 10. Acker DB. A shoulder dystocia intervention form. Obstet Gynecol 1991;78:150 – 1. Deering S, Poggi S, Hodor J, et al. Evaluation of residents’ delivery notes after a simulated shoulder dystocia. Obstet Gynecol 2004;104:667 – 70. Gherman RB, Ouzounian JG, Goodwin TM. Obstetrical maneuvers for shoulder dystocia and associated fetal morbidity. Am J Obstet Gynecol 1998;178:1126 – 30. Gherman RB, Ouzounian JG, Satin AJ, et al. A comparison of shoulder dystocia-associated transient and permanent brachial plexus palsies. Obstet Gynecol 2003;102:544 – 8. Thompson KA, Satin AJ, Gherman RB. Spiral fracture of the radius: an unusual case of shoulder dystocia-associated morbidity. Obstet Gynecol 2003;102:36 – 8. Nocon JJ, McKenzie DK, Thomas LJ, et al. Shoulder dystocia: an analysis of risks and obstetric maneuvers. Am J Obstet Gynecol 1993;168:1732 – 9. Nesbitt TS, Gilbert WM, Herrchen B. Shoulder dystocia and associated risk factors with macrosomic infants born in California. Am J Obstet Gynecol 1998;179:476 – 80. Acker DB, Sachs BP, Friedman EA. Risk factors for shoulder dystocia. Obstet Gynecol 1985; 66:762 – 8. Geary M, McParland P, Johnson H, et al. Shoulder dystocia: is it predictable? Eur J Obstet Gynecol Reprod Biol 1995;62:15 – 8. Lewis DF, Edwards MS, Asrat T, et al. Can shoulder dystocia be predicted? Preconceptive and prenatal factors. J Reprod Med 1998;43:654 – 8. Robinson H, Tkatch S, Mayes DC, et al. Is maternal obesity a predictor of shoulder dystocia? Obstet Gynecol 2003;101:24 – 7. American College of Obstetricians and Gynecologists. Fetal macrosomia. Practice Bulletin No.22. Washington, DC7 American College of Obstetricians and Gynecologists; 2000. American College of Obstetricians and Gynecologists. Shoulder dystocia. Practice Bulletin No. 40. Washington, DC7 American College of Obstetricians and Gynecologists; 2002. Flamm B. Tight nuchal cord and shoulder dystocia: a potentially catastrophic combination. Obstet Gynecol 1999;94:853. Beall MH, Spong CY, Ross MG. A randomized controlled trial of prophylactic maneuvers to reduce head-to-body time in patients at risk for shoulder dystocia. Obstet Gynecol 2003; 102:31 – 5. Poggi SH, Allen RH, Patel CR, et al. Randomized trial of McRoberts vs. lithotomy positioning to decrease the force that is applied to the fetus during delivery. Am J Obstet Gynecol 2004;191:874 – 8. Gherman RB, Tramont J, Muffley P, et al. Analysis of McRoberts’ maneuver by X-ray pelvimetry. Obstet Gynecol 2000;95:43 – 7. Gurewitsch ED, Donithan M, Stallings SP, et al. Episiotomy versus fetal manipulation in managing severe shoulder dystocia: a comparison of outcomes. Am J Obstet Gynecol 2004; 191:911 – 6. Hankins GDV. Lower thoracic spinal cord injury: a severe complication of shoulder dystocia. Am J Perinatol 1998;15:443 – 4. Penney DS, Perlis DW. Shoulder dystocia: when to use suprapubic pressure. MCN Am J Matern Child Nurs 1992;17:34 – 6. Stallings SP, Edwards RK, Johnson JWC. Correlation of head-to-body delivery intervals in shoulder dystocia and umbilical artery acidosis. Am J Obstet Gynecol 2001;185:268 – 74. Poggi SH, Spong CY, Allen RH. Priortizing posterior arm delivery during severe shoulder dystocia. Obstet Gynecol 2003;101:1068 – 72. Zelig CM, Gherman RB. Modified Zavanelli maneuver for the alleviation of shoulder dystocia. Obstet Gynecol 2002;100:1112 – 4. Bruner JP, Drummond SB, Meenan AL, et al. All-fours maneuver for reducing shoulder dystocia during labor. J Reprod Med 1998;43:439 – 43.
Shoulder Dystocia: Prevention and Management Robert B. Gherman, MD* Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, Washington Adventist Hospital, 7600 Carrou Avenue, 3rd floor, Takoma Park, MD 20912, USA
Despite its infrequent occurrence (0.2%–3% of all deliveries), all health care providers who attend vaginal deliveries must be prepared to handle this unpredictable obstetric emergency [1]. Shoulder dystocia represents the failure of delivery of the fetal shoulders, whether it be the anterior, posterior, or both fetal shoulders [2]. Shoulder dystocia results from a size discrepancy between the fetal shoulders and the pelvic inlet. A persistent anteroposterior location of the fetal shoulders at the pelvic brim occurs when there is increased resistance between the fetal skin and vaginal walls (eg, with macrosomia), with a large fetal chest relative to the biparietal diameter, and when truncal rotation does not occur (eg, precipitous labor) [3]. Shoulder dystocia also can occur from impaction of the posterior fetal shoulder on the maternal sacral promontory. Most authors have defined this obstetric emergency to include deliveries that require maneuvers in addition to gentle downward traction on the fetal head to effect delivery. Several studies have proposed defining shoulder dystocia as a prolonged head-to-body delivery interval (60 seconds) or the use of ancillary obstetric maneuvers, because this time represented the mean plus two standard deviations [4,5].
Maternal and fetal risks Postpartum hemorrhage and the unintentional extension of an episiotomy or laceration into the rectum (fourth-degree laceration) are the most common
* 21636 Ripplemead Drive, Laytonsville, MD 20882. E-mail address: [email protected] 0889-8545/05/$ – see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.ogc.2004.12.006
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maternal complications associated with shoulder dystocia. In the study by Gherman et al [6], these complications occurred in 11% and 3.8%, respectively, of the described shoulder dystocias. Other complications that have been reported have included vaginal lacerations, cervical tears, bladder atony, and uterine rupture. Maternal symphyseal separation and lateral femoral cutaneous neuropathy also have been associated with overly aggressive hyperflexion of the maternal legs [7]. Risks to the physician mainly involve litigation, because brachial plexus palsy, central neurologic dysfunction, and perinatal death account for most of the shoulder dystocia–related lawsuits. A clearly documented medical record may prove to be helpful in the medicolegal arena (Box 1) [8,9]. A large retrospective study that evaluated 285 cases of shoulder dystocia found that the fetal injury rate was 24.9%, including 48 (16.8%) brachial plexus palsies, 27 (9.5%) clavicular fractures, and 12 (4.2%) humeral fractures [10]. Unilateral brachial plexus injuries have represented the most common neurologic injury sustained by neonates. The right arm is usually affected (64.6%) because the left occiput anterior presentation leaves the right shoulder impinged against the symphysis pubis [10]. Brachial plexus injury has been found to complicate up to 21% of all cases of shoulder dystocia [11]. Most (80%) of these nerve injuries have been located within C5-C6 nerve roots (Erb-Duchenne palsy). Other types of brachial plexus injuries that have been described include Klumpke’s palsy (C8-T1), an intermediate palsy, and complete palsy of the entire brachial plexus. Diaphragmatic paralysis, Horner’s syndrome, and facial nerve injuries have been reported to occasionally accompany brachial plexus palsy [3]. Approximately one third of brachial plexus palsies are associated with
Box 1. Suggested medicolegal documentation for shoulder dystocia When and how dystocia was diagnosed Progress of labor (active phase and second stage) Position and rotation of the infant’s head Presence of episiotomy, if performed Anesthesia required Estimation of force of traction applied Order, duration, and results of maneuvers used Duration of shoulder dystocia Documentation of adequate pelvimetry before initiating labor induction or augmentation Neonatal and obstetric impressions of the infant after delivery Information given to gravida that shoulder dystocia had occurred Data from Acker DB. A shoulder dystocia intervention form. Obstet Gynecol 1991;78:150–1.
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Table 1 Common complications associated with shoulder dystocia Maternal
Accoucheur
Neonatal
Third- or fourth-degree lacerations Postpartum hemorrhage
Terror Medical liabilty
Erb’s palsy Klumpke’s palsy Clavicular fracture Humeral fracture Hypoxia Permanent brain injury Death
a concomitant bone fracture, most commonly the clavicle (94%) [8]. Neonatal radial fracture also can be associated with shoulder dystocia or the maneuvers used for the alleviation of shoulder dystocia [12]. The study by Gherman et al [10] compared shoulder dystocia cases based on the absence or presence of direct fetal manipulative maneuvers (Woods, posterior arm extraction, or Zavanelli). They found that the overall incidence of fetal bone fracture (16.5% versus 11.4%; P = 0.21) and brachial plexus palsy (21.3% versus 13.3%; P = 0.1) were not different between the two groups. Similar findings previously were been reported by Nocon et al [13], who grouped techniques used to disimpact the shoulder into major treatment categories. None of the major categories revealed a statistically significant difference when compared with respect to fetal injury. In this study, the authors found incidences of injury of 14.9%, 14.3%, 37.9%, and 20%, respectively, associated with McRoberts, rotations, posterior arm delivery, and suprapubic pressure (Table 1).
Prenatal: identifying the pregnancy at risk Research clearly has shown that there is a significantly increased risk of shoulder dystocia as birth weight increases. The percentages of births complicated by shoulder dystocia for unassisted births not complicated by diabetes were 5.2% for infants who weighed 4000 to 4250 g, 9.1% for infants 4250 to 4500 g, 14.3% for infants 4500 to 4750 g, and 21.1% for infants 4750 to 5000 g [14]. One must remember, however, that approximately 50% to 60% of cases of shoulder dystocia occur in infants who weigh less than 4000 g. Even if the birth weight of an infant is more than 4000 g, shoulder dystocia complicates only 3.3% of the deliveries [15,16]. From a prospective point of view, prepregnancy and antepartum risk factors, such as previous delivery of an infant with macrosomia, pre-existing or pregnancy-induced diabetes mellitus, multiparity, excessive maternal weight gain, and post-date gestation, have exceedingly poor predictive value for the prediction of shoulder dystocia. For example, one study found that only 32% of patients were obese (N 90 kg), 25% had excessive weight gain (N 20 kg), 8%
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had short stature (b 60 in), 6% were more than 42 weeks’ gestation, 3% were of advanced maternal age, and 2% had a personal history of diabetes mellitus [17]. In a case control study from the Northern and Central Alberta Perinatal Outreach Program, maternal obesity (defined as more than 91 kg) was not associated with shoulder dystocia when multivariable logistic regression analysis was used to control for confounding effects [18]. Ultrasonographic estimation of fetal weight, performed during either the late third trimester or the intrapartum period, has been used commonly to estimate the risk of shoulder dystocia via prediction of birth weight. To date, however, no studies have evaluated this relationship specifically in a patient population in which routine ultrasounds are performed. Late pregnancy ultrasound likewise displays low sensitivity (22%–44%), exceedingly poor positive predictive value (30%–44%), decreasing accuracy with increasing birth weight, and an overall tendency to overestimate the birth weight. For this reason, the American College of Obstetrician and Gynecologists recently noted that attempted vaginal delivery is not contraindicated for women with estimated fetal weights up to 5000 g in the absence of maternal diabetes [19,20]. Patients with insulin-requiring diabetes mellitus seem to warrant special evaluation for shoulder dystocia. The risk of shoulder dystocia for unassisted births to mothers with diabetes has been found to be 8.4%, 12.3%, 19.9%, and 23.5% when the birth weight is 4000 to 4250 g, 4250 to 4500 g, 4500 to 4750 g, or more than 4750 g, respectively [14]. Changes in fetal body configuration (eg, larger trunk and chest circumferences, increased bisacromial diameters, and chest-to-head disproportion) do not allow the fetal shoulders to rotate into the oblique diameter. In a similar fashion, patients with a history of shoulder dystocia that complicated a prior vaginal delivery merit consideration for recurrence. Recurrence risks for shoulder dystocia range between 11.9% and 16.7%. Maternal and fetal factors that have been shown to be significantly associated with recurrent shoulder dystocia include birth weight more than the index pregnancy, time in the second stage of labor, and birth weight more than 4000 g [1]. A policy of universal elective cesarean delivery has not been recommended for this cohort of patients [20]; however, antepartum counseling and discussion of recurrence risks should be undertaken with consideration of the current estimate of fetal weight, the presence of maternal glucose intolerance, and whether the prior shoulder dystocia resulted in transient or permanent neurologic injury. Practical management of shoulder dystocia Shoulder dystocia usually is heralded by the classic ‘‘turtle sign’’; after the fetal head is delivered, it retracts back tightly against the maternal perineum. Shoulder dystocia, however, typically is not diagnosed until attempts at downward traction have been unsuccessful in delivering one or both shoulders. The patient should be instructed to stop pushing after the shoulder dystocia is initially recognized. Maternal expulsive efforts, however, must be reinstituted
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after the fetal shoulders have been converted to the oblique diameter to achieve delivery. If the provider is alone, additional assistance may be provided by summoning other obstetricians, an anesthetist or anesthesiologist, additional nursing support, and a pediatrician. Umbilical cord compression, most commonly between the fetal body and maternal pelvis, leads to a decrease in the fetal pH at a rate of 0.04 U/min. If a nuchal cord is present and cannot be reduced easily over the fetal head, clamping and cutting of the cord should be avoided until the shoulder dystocia has been alleviated [21]. Most, if not all, of the commonly encountered shoulder dystocia episodes are able to be relieved within several minutes. Although research studies have been unable to predict an exact time limit at which irreversible brain injury occurs, it is reasonable to assume that the risk of permanent central neurologic dysfunction is associated with prolongation of the head/ shoulder interval thresholds. At the time of delivery, if shoulder dystocia is a concern, some clinicians have empirically advocated immediately proceeding to delivery of the fetal shoulders to maintain the forward momentum of the fetus. Others support a short delay in delivery of the shoulders, arguing that the endogenous rotational mechanics of the second stage may spontaneously alleviate the obstruction. Obstetricians also may use the McRoberts’ maneuver ‘‘prophylactically’’ to decrease the risk of shoulder dystocia or shorten the second stage of labor. A clinical trial randomized patients with estimated fetal weights more than 3800 g to undergo either prophylactic maneuvers (ie, McRoberts maneuver and suprapubic pressure) or maneuvers only after delivery of the fetal head, if shoulder dystocia was identified. This study, however, found that head-to-body delivery times, an indirect proxy for shoulder dystocia, did not differ between the prophylactic and control patients [22]. The use of the McRoberts’ maneuver before the clinical diagnosis of shoulder dystocia does not significantly change the traction forces applied to the fetal head during vaginal delivery in multiparous patients [23]. Although many maneuvers have been described for the successful alleviation of shoulder dystocia (Box 2), no randomized controlled trials or laboratory experiments have compared these techniques directly. Most obstetricians currently use the McRoberts’ maneuver as their initial step for the disimpaction of the shoulder. In a retrospective review of 236 shoulder dystocia cases that occurred between 1991 and 1994 at Los Angeles County/University of Southern California Medical Center, this maneuver alone alleviated 42% of cases. Trends toward lower rates of maternal and neonatal morbidity also were associated with the McRoberts’ maneuver [6]. The McRoberts’ maneuver, performed by sharply flexing the maternal thighs onto the abdomen, results in a straightening of the maternal sacrum relative to the lumbar spine with consequent cephalic rotation of the symphysis pubis [24]. Care should be taken to avoid prolonged or overly aggressive application of the McRoberts’ maneuver because the fibrocartilaginous articular surfaces of the symphysis pubis and surrounding ligaments may be stretched unduly.
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Box 2. Maneuvers for the alleviation of shoulder dystocia Maternal hip hyperflexion (McRoberts’ maneuver) Suprapubic pressure Rotational maneuvers Wood’s maneuver Rubin’s maneuver Delivery of the posterior arm (Barnum maneuver) ‘‘All fours’’ (Gaskin maneuver) Cephalic replacement Zavanelli Modified Zavanelli Symphysiotomy Abdominal rescue through hysterotomy
Most patients can assume the proper position for the McRoberts’ maneuver with little difficulty. Women may be instructed to grasp the posterior aspect of their thighs and pull themselves into position, with family members or health care professionals providing any assistance necessary. An obstetrician also may choose to flex both of the patient’s legs. Problems may occur when moving an obese patient or a woman who has undergone a dense epidural motor blockade. Because shoulder dystocia is considered to be a ‘‘bony dystocia,’’ episiotomy alone does not release the impacted shoulder. The need for cutting a generous episiotomy or procto-episiotomy must be based on clinical circumstances, such as a narrow vaginal fourchette in a primigravida patient. This procedure may allow the fetal rotational maneuvers to be performed with ease and create more room for attempted delivery of the posterior arm. Management by episiotomy or procto-episiotomy is associated with a nearly sevenfold increase in the rate of severe perineal trauma without benefit of reducing the occurrence of neonatal depression or brachial plexus palsy [25]. All attendants should refrain from applying fundal pressure as a maneuver for the alleviation of the shoulder dystocia. Pushing on the fundus simply duplicates a maternal directional expulsive force that already has failed to deliver the fetal shoulder and serves only to impact further the anterior shoulder behind the symphysis pubis. The use of fundal pressure also has been associated with an increased risk of Erb’s palsy and thoracic spinal cord injury in the neonate [26]. Suprapubic pressure, commonly administered by nursing personnel, is typically given immediately before or in direct conjunction with the McRoberts’ maneuver. This pressure usually is directed posteriorly in an attempt to force the anterior shoulder under the symphysis pubis. Other described techniques for suprapubic pressure have included lateral application from either side of the maternal abdomen and alternating between sides using a rocking pressure [27].
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Many cases of shoulder dystocia require the performance of several maneuvers to alleviate the impaction. Stallings et al [28] found that slightly more than one third of patients required more than two maneuvers. When more complex maneuvers are required, either fetal rotational maneuvers or posterior arm extraction may be used. In the Woods’ corkscrew maneuver, the practitioner attempts to abduct the posterior shoulder by exerting pressure onto the anterior surface of the posterior shoulder. In the Rubin’s (reverse Woods’) maneuver, pressure is applied to the posterior surface of the most accessible part of the fetal shoulder (ie, either the anterior or posterior shoulder) to effect shoulder adduction. These rotational maneuvers, however, may be difficult to perform when the anterior shoulder is tightly wedged underneath the symphysis pubis. It may be necessary to push the fetus slightly upward to facilitate the rotation. By replacing the bisacromial diameter with the axillo-acromial diameter, posterior arm delivery creates a 20% reduction in shoulder diameter [29]. To perform delivery of the posterior fetal arm, pressure should be applied by the delivering provider at the antecubital fossa to flex the fetal forearm. The arm is subsequently swept out over the infant’s chest and delivered over the perineum. Rotation of the fetal trunk to bring the posterior arm anteriorly is sometimes required. Grasping and pulling directly on the fetal arm and applying pressure onto the mid-humeral shaft should be avoided because bone fracture may occur. The previously mentioned maneuvers typically are able to be attempted within 4 to 5 minutes after identification of the shoulder dystocia. If the shoulder dystocia remains undelivered, a bilateral shoulder dystocia or posterior arm shoulder dystocia may be present. The latter is suggested by the presence of the posterior arm being maintained at the level of the pelvic inlet and an inability to perform posterior arm extraction. These intractable shoulder dystocias warrant the performance of heroic techniques, such as the Zavanelli maneuver, symphysiotomy, or hysterotomy. Performance of these maneuvers is complicated by a provider’s lack of clinical experience with these maneuvers, performance under emergent conditions, and significant maternal and neonatal complications inherent in the procedures. In the Zavanelli maneuver, the head is rotated back to a prerestitution position and then gently flexed. Constant firm pressure is used to push the head back into the vagina and cesarean delivery is subsequently performed. Halothane or other general anesthetic agents, in conjunction with tocolytic agents, may be administered in preparation for and during the Zavanelli maneuver. Oral or intravenous nitroglycerin also may be used. The modification of the original Zavanelli maneuver may be used to potentially reduce maternal morbidity. As described by Zelig and Gherman [30], maternal expulsive efforts were initiated after the obstetricians observed that the biparietal diameter had passed back through the introitius and the shoulders were felt to disimpact. This modification should be attempted only as long as no evidence of intrauterine fetal compromise exists. To perform a symphysiotomy, the patient should be placed in an exaggerated lithotomy position. Although its placement may be difficult secondary to
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obstruction, a Foley catheter can help to identify the urethra. With the physician’s index and middle finger displacing the urethra laterally, the cephalad portion of the symphysis is incised with a scalpel blade or Kelly clamp. Hysterotomy also may be performed either to resolve the shoulder dystocia primarily or assist with vaginal techniques. The posterior fetal arm may be delivered through the transverse uterine incision with subsequent passage of the hand to a vaginal assistant. The abdominal surgeon can apply pressure on the anterior fetal shoulder to allow rotation to the oblique diameter. Before performing these techniques, one may consider using the ‘‘all-fours’’ technique, in which the patient is rolled from her existing position onto her hands and knees [31]. The downward force of gravity or a favorable change in pelvic diameters produced by this maneuver may allow disimpaction of the fetal shoulder. Older textbooks have described deliberate clavicular fracture as a maneuver of last resort, performed by exerting direct upward pressure on the mid-portion of the fetal clavicle. In reality, however, this has not been reported in the recent literature because it is technically difficult to perform and risks serious injury to the underlying vascular and pulmonary structures in the fetus.
Summary Knowledge of the maneuvers used for the alleviation of shoulder dystocia is relevant not only for obstetric residents and attending house staff but also for family practitioners, nurses, and nurse midwives. The performance of shoulder dystocia ‘‘drills’’ can be helpful not only to coordinate a teamwork approach to this obstetric emergency but also provide an opportunity to practice the maneuvers. Shoulder dystocia continues to represent an immense area of clinical interest because it typically occurs without prediction. All patients in labor should be considered at risk for developing shoulder dystocia.
References [1] Gherman RB. Shoulder dystocia: an evidence-based evaluation of the obstetric nightmare. Clin Obstet Gynecol 2002;45:345 – 62. [2] Collins JH, Collins CL. What is shoulder dystocia? J Reprod Med 2001;46:148 – 9. [3] Gherman RB, Ouzounian JG, Goodwin TM. Brachial plexus palsy: an in utero injury? Am J Obstet Gynecol 1999;180:1303 – 7. [4] Spong CY, Beall M, Rodrigues D, et al. An objective definition of shoulder dystocia: prolonged head-to-body delivery intervals and/or the use of ancillary obstetric maneuvers. Obstet Gynecol 1995;86:433 – 6. [5] Beall MH, Spong C, McKay J, et al. Objective definition of shoulder dystocia: a prospective evaluation. Am J Obstet Gynecol 1998;179:934 – 7. [6] Gherman RB, Goodwin TM, Souter I, et al. The McRoberts’ maneuver for the alleviation of shoulder dystocia: how successful is it? Am J Obstet Gynecol 1997;176:656 – 61. [7] Gherman RB, Ouzounian JG, Incerpi MH, et al. Symphyseal separation and transient femo-
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[8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22]
[23]
[24] [25]
[26] [27] [28] [29] [30] [31]
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ral neuropathy associated with the McRoberts’ maneuver. Am J Obstet Gynecol 1998;178: 609 – 10. Acker DB. A shoulder dystocia intervention form. Obstet Gynecol 1991;78:150 – 1. Deering S, Poggi S, Hodor J, et al. Evaluation of residents’ delivery notes after a simulated shoulder dystocia. Obstet Gynecol 2004;104:667 – 70. Gherman RB, Ouzounian JG, Goodwin TM. Obstetrical maneuvers for shoulder dystocia and associated fetal morbidity. Am J Obstet Gynecol 1998;178:1126 – 30. Gherman RB, Ouzounian JG, Satin AJ, et al. A comparison of shoulder dystocia-associated transient and permanent brachial plexus palsies. Obstet Gynecol 2003;102:544 – 8. Thompson KA, Satin AJ, Gherman RB. Spiral fracture of the radius: an unusual case of shoulder dystocia-associated morbidity. Obstet Gynecol 2003;102:36 – 8. Nocon JJ, McKenzie DK, Thomas LJ, et al. Shoulder dystocia: an analysis of risks and obstetric maneuvers. Am J Obstet Gynecol 1993;168:1732 – 9. Nesbitt TS, Gilbert WM, Herrchen B. Shoulder dystocia and associated risk factors with macrosomic infants born in California. Am J Obstet Gynecol 1998;179:476 – 80. Acker DB, Sachs BP, Friedman EA. Risk factors for shoulder dystocia. Obstet Gynecol 1985; 66:762 – 8. Geary M, McParland P, Johnson H, et al. Shoulder dystocia: is it predictable? Eur J Obstet Gynecol Reprod Biol 1995;62:15 – 8. Lewis DF, Edwards MS, Asrat T, et al. Can shoulder dystocia be predicted? Preconceptive and prenatal factors. J Reprod Med 1998;43:654 – 8. Robinson H, Tkatch S, Mayes DC, et al. Is maternal obesity a predictor of shoulder dystocia? Obstet Gynecol 2003;101:24 – 7. American College of Obstetricians and Gynecologists. Fetal macrosomia. Practice Bulletin No.22. Washington, DC7 American College of Obstetricians and Gynecologists; 2000. American College of Obstetricians and Gynecologists. Shoulder dystocia. Practice Bulletin No. 40. Washington, DC7 American College of Obstetricians and Gynecologists; 2002. Flamm B. Tight nuchal cord and shoulder dystocia: a potentially catastrophic combination. Obstet Gynecol 1999;94:853. Beall MH, Spong CY, Ross MG. A randomized controlled trial of prophylactic maneuvers to reduce head-to-body time in patients at risk for shoulder dystocia. Obstet Gynecol 2003; 102:31 – 5. Poggi SH, Allen RH, Patel CR, et al. Randomized trial of McRoberts vs. lithotomy positioning to decrease the force that is applied to the fetus during delivery. Am J Obstet Gynecol 2004;191:874 – 8. Gherman RB, Tramont J, Muffley P, et al. Analysis of McRoberts’ maneuver by X-ray pelvimetry. Obstet Gynecol 2000;95:43 – 7. Gurewitsch ED, Donithan M, Stallings SP, et al. Episiotomy versus fetal manipulation in managing severe shoulder dystocia: a comparison of outcomes. Am J Obstet Gynecol 2004; 191:911 – 6. Hankins GDV. Lower thoracic spinal cord injury: a severe complication of shoulder dystocia. Am J Perinatol 1998;15:443 – 4. Penney DS, Perlis DW. Shoulder dystocia: when to use suprapubic pressure. MCN Am J Matern Child Nurs 1992;17:34 – 6. Stallings SP, Edwards RK, Johnson JWC. Correlation of head-to-body delivery intervals in shoulder dystocia and umbilical artery acidosis. Am J Obstet Gynecol 2001;185:268 – 74. Poggi SH, Spong CY, Allen RH. Priortizing posterior arm delivery during severe shoulder dystocia. Obstet Gynecol 2003;101:1068 – 72. Zelig CM, Gherman RB. Modified Zavanelli maneuver for the alleviation of shoulder dystocia. Obstet Gynecol 2002;100:1112 – 4. Bruner JP, Drummond SB, Meenan AL, et al. All-fours maneuver for reducing shoulder dystocia during labor. J Reprod Med 1998;43:439 – 43.