Shoulder dystocia is one of the most dreaded and dramatic complications encountered in obstetrics. It is a true emergency that can lead to high rates of maternal morbidity as well as neonatal morbidity and mortality. Various maneuvers can free the impacted shoulder to obviate fetal hypoxia. The steps are completed expeditiously, but mechanical force must be tempered to avoid maternal and fetal traumatic injury. The importance of this obstetric complication and its sequelae were emphasized by the appointment of a Task Force by American College of Obstetricians and Gynecologists president Dr. James T. Breeden. This working group published its monograph Neonatal Brachial Plexus Palsy in 2014.
Shoulder dystocia has been defined in several ways. Following complete emergence of the fetal head during vaginal delivery, the remainder of the body may not rapidly follow despite downward traction and maternal pushing. Resnik (1980) described shoulder dystocia as a condition requiring special maneuvers to deliver the shoulders following an unsuccessful attempt to apply downward traction. Benedetti (1989) more specifically defined it as an arrest of spontaneous delivery due to impaction of the anterior shoulder behind and against the symphysis pubis. The Task Force cited a commonly accepted definition that requires additional maneuvers following failure of gentle downward traction on the fetal head to deliver the shoulders. Other investigators use the head-to-body time interval as the defining factor (Beall, 1998; Hoffman, 2011). Spong and coworkers (1995) reported that the mean head-to-body delivery time in normal births was 24 seconds compared with 79 seconds in those with shoulder dystocia. These investigators proposed that head-to-body delivery time >60 seconds should define shoulder dystocia.
At this time, it is reasonable for the diagnosis to continue to rely on the clinical perception that the normal downward traction needed for fetal shoulder delivery is ineffective. But, whatever definition is used, any perceived shoulder dystocia is an obstetric emergency. The umbilical cord is compressed within the birth canal, and the placenta is variably separated.
Shoulder dystocia has been described in the medical literature for at least two centuries. Swartz (1960) quoted Smellie, writing in 1730: "A sudden call to a gentlewoman in labor. The child's head delivered for a long time—but even with hard pulling from the midwife, the remarkably large shoulder prevented delivery. I have been called by midwives to many cases of this kind, in which the child was frequently lost." In his premier edition of Obstetrics, J. Whitridge Williams (1903) warns against applying excessive traction to avert traumatic brachial plexus stretching. But even as late as 1966, shoulder dystocia received relatively little attention. For example, in the 13th edition of Williams Obstetrics by Eastman and Hellman (1966), only one page is devoted to the subject. By way of contrast, this entire contemporaneous chapter is devoted to shoulder dystocia and its management.