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Shoulder dystocia is a rare obstetric emergency that immediately places the mother and the fetus at risk for significant morbidity and mortality. It is diagnosed when, after delivery of the fetal head, further expulsion of the fetus is prevented by impaction of the fetal shoulders within the maternal pelvis.1Shoulder dystocia is considered an emergent situation that the clinician must recognize and quickly respond to by properly delivering the fetus.

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The incidence of shoulder dystocia varies from less than 1 to 4 percent of cephalic spontaneous vaginal deliveries.2–7 Differing definitions of shoulder dystocia may account for some of this variability. Some reports require that maneuvers for shoulder release be documented on the chart whereas others accept the physician’s clinical diagnosis of shoulder dystocia. Other definitions look at the timing of the delivery of the head, the delivery of the shoulders, or the completion of the birth. The rare occurrences of shoulder dystocia make design of prospective studies difficult, both in describing the incidence and in evaluating the efficacy of various release maneuvers.8

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Shoulder dystocia may not be anticipated in advance. Many risk factors are associated with shoulder dystocia. However, many patients with shoulder dystocia have none of these risk factors. Emergency Physicians usually do not have knowledge of the patient’s prenatal history, ultrasound reports, or previous deliveries. This makes it difficult to predict shoulder dystocia. It is imperative for the Emergency Physician to be knowledgeable and comfortable with release maneuvers in the event they encounter shoulder dystocia during a precipitous delivery.

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Shoulder dystocia is usually diagnosed when, after delivery of the fetal head, the fetal shoulders fail to deliver despite standard gentle traction on the fetal head. It results from impingement of the biacromial diameter of the fetus against the maternal pubic symphysis anteriorly and the maternal sacral promontory posteriorly.9

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Shoulder dystocia is a rare and potentially catastrophic obstetrical emergency. The clinician must deliver the fetus quickly and without applying excessive forces that may result in fetal injury. Always be prepared for the possibility of shoulder dystocia. Recognize the possible associated risk factors that include fetal macrosomia, maternal diabetes, a prior history of shoulder dystocia or macrosomia, prolonged second stage of labor, post-term pregnancy, multiparity, obesity, and operative vaginal delivery from the midpelvis.9

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Fetal macrosomia is defined as fetal growth beyond a specific weight, usually 4000 to 4500 gm, regardless of the fetal gestational age. The risk of shoulder dystocia is 9.2 to 24 percent in nondiabetic pregnant women, and 19.9 to 50 percent in diabetic women when birth weight is greater than 4500 grams.10 The ability to predict fetal macrosomia is limited. Shoulder dystocia can occur unexpectedly in infants of normal birth weights.10 A simple algorithm to help determine if shoulder dystocia or fetal macrosomia may be present is shown in Figure 112-1.

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