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Shoulder dystocia: Risk factors and planning delivery of at risk pregnancies

John F Rodis, MD
Section Editor
Charles J Lockwood, MD, MHCM
Deputy Editor
Vanessa A Barss, MD, FACOG


A vaginal delivery is complicated by shoulder dystocia when, after delivery of the fetal head, additional obstetric maneuvers beyond gentle guidance are needed to enable delivery of the fetal shoulders. It occurs when the fetal bisacromial diameter descends in an anterior-posterior instead of an oblique position. The anterior shoulder then impacts behind the maternal symphysis pubis or, less commonly, the posterior shoulder impacts behind the sacral promontory.

Risk factors for shoulder dystocia and planning delivery of pregnancies at risk will be discussed here. Intrapartum diagnosis, management, and outcome of shoulder dystocia are reviewed separately. (See "Shoulder dystocia: Intrapartum diagnosis, management, and outcome".)


Shoulder dystocia occurs in 0.2 to 3 percent of births and represents an obstetric emergency [1]. Brachial plexus injury (commonly called an Erb’s palsy) is one of the most serious neonatal complications, and occurs in 2 to 16 percent of shoulder dystocias. Most cases resolve, but up to 30 percent result in permanent neurologic impairment [2-4]. Other complications include neonatal clavicular fracture and maternal anal sphincter laceration. (See "Shoulder dystocia: Intrapartum diagnosis, management, and outcome", section on 'Complications'.)


The occurrence of shoulder dystocia cannot be accurately predicted by antenatal or intrapartum risk factors (see 'Risk factors' below) or imaging studies (see 'Pelvimetry and fetal biometry' below). Since at least 50 percent of pregnancies complicated by shoulder dystocia have no identifiable risk factors, the predictive value of any one or combination of risk factors for shoulder dystocia is low (less than 10 percent) [1,5-7]. Therefore, all obstetric care providers should be able to (1) promptly recognize when gentle traction alone is inadequate for delivery of the shoulders and (2) proceed through an orderly sequence of maneuvers to deliver the neonate in a timely manner, with no or minimal maternal and fetal trauma. It should be noted, however, that permanent birth injury, and even fetal death, can result in cases of shoulder dystocia that are appropriately identified and managed. (See "Shoulder dystocia: Intrapartum diagnosis, management, and outcome".)

Risk factors — High birth weight is the major risk factor for shoulder dystocia. Although other risk factors have also been associated with shoulder dystocia, they are often related to high birth weight. The increasing prevalence of risk factors such as maternal obesity, diabetes, and older age at first birth may be associated with an increased prevalence of shoulder dystocia [8,9].


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Literature review current through: May 2017. | This topic last updated: Mar 27, 2017.
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