Williams Manual of Pregnancy Complications, 23 ed.

CHAPTER 16. Shoulder Dystocia

The incidence of shoulder dystocia varies between 0.6 and 1.4 percent, depending on the criteria used, with a lower incidence reported when the diagnosis does not require the use of maneuvers to relieve the dystocia. Although the risk of shoulder dystocia is related to infant size, many cases occur in infants whose size is not considered excessive (Table 16-1). There is evidence that the incidence of shoulder dystocia has increased over time due to increasing birthweight.

TABLE 16-1. Incidence of Shoulder Dystocia According to Birthweight Grouping in Singleton Infants Delivered Vaginally in 1994 at Parkland Hospital

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MATERNAL CONSEQUENCES

Postpartum hemorrhage usually not only from uterine atony but also from vaginal and cervical lacerations is the major maternal risks from shoulder dystocia.

FETAL CONSEQUENCES

Shoulder dystocia may be associated with significant fetal morbidity and even mortality. Between 17 and 25 percent of shoulder dystocias are associated with fetal injury and this is typically due to brachial plexus injury, most of which resolves without sequela.

Up to 25 percent of shoulder dystocias are associated with significant fetal morbidity and in some cases mortality. The majority of these are transient brachial plexus injuries without sequelae.

PREDICTION AND PREVENTION OF SHOULDER DYSTOCIA

There has been considerable evolution in obstetrical thinking about the preventability of shoulder dystocia in the past two decades. Although several risk factors are clearly associated with shoulder dystocia, actual identification of individual cases before the fact has proven to be impossible.

Recognizing the role birthweight plays in the etiology of shoulder dystocia, the American College of Obstetricians and Gynecologists (Shoulder dystocia, Practice Bulletin No. 40, November 2002) has published the following guidelines: (1) Most cases of shoulder dystocia cannot be predicted or prevented because there are no accurate methods to identify which fetuses will develop this complication. (2) Ultrasonic measurements to estimate macrosomia have limited accuracy. (3) Elective induction of labor or planned cesarean delivery based on suspected macrosomia is not a reasonable strategy. (4) Planned cesarean delivery may be reasonable for the diabetic woman with an estimated fetal weight exceeding 4500 g.

MANAGEMENT OF SHOULDER DYSTOCIA

Because shoulder dystocia cannot be predicted, the practitioner of obstetrics must be well versed in the management principles of this occasionally devastating delivery complication. Reduction in the interval of time from delivery of the head to delivery of the body is of great importance to survival. An initial gentle attempt at traction, assisted by maternal expulsive efforts is recommended. Overly vigorous traction on the head or neck, or excessive rotation of the body, may cause serious damage to the infant.

Some have advocated performing a large episiotomy, and adequate analgesia is certainly ideal. The next step is to clear the infant’s mouth and nose. Having completed these steps, a variety of techniques have been described to free the anterior shoulder from its impacted position beneath the maternal symphysis pubis.

shoulder dystocia drill helps better organize emergency management of an impacted shoulder. The drill is a set of maneuvers performed sequentially as needed to complete vaginal delivery. The American College of Obstetricians and Gynecologists (Fetal macrosomia, Practice Bulletin No. 22, November 2000) recommends the steps shown in Table 16-2.

TABLE 16-2. Shoulder Dystocia Drill for Emergency Management of an Impacted Shoulder

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For further reading in Williams Obstetrics, 23rd ed.,

see Chapter 20, “Dystocia: Abnormal Labor.”