Shoulder dystocia occurs in 0.2% to 3.0% of all vaginal deliveries and is defined as an impaction of the fetal shoulder after delivery of the head. It is associated with increased fetal morbidity and mortality secondary to brachial plexus injuries and fetal asphyxia. The diagnosis should be considered when the application of gentle, downward pressure of the fetal head fails to accomplish delivery.
Macrosomia is associated with shoulder dystocia. With infants weighing >4500 g, the risk of shoulder dystocia has been reported to be 9% to 14%. When maternal diabetes is factored in with weight >4500 g, the incidence is as high as 20% to 50%.
Other risk factors include maternal obesity, previous macrosomic infant, diabetes mellitus, and gestational diabetes. However, it should be noted that most cases occur in nondiabetic women with normal-sized infants. Clinicians should be aware of the risk factors, but a level of caution should be extended to all patients.
Anticipation and preparation are important. Help should be available as extra hands may be needed during the delivery. A pediatrician should be notified. If available, an anesthesiologist should also be informed.
The time should be marked when the dystocia is called, if Pitocin has been used, it should be discontinued, and the total time until delivery recorded in the notes. Once the shoulder dystocia is identified, no significant downward pressure should be applied to the head until the shoulders are delivered. Fundal pressure should never be applied as it only exacerbates the shoulder impaction.
McRoberts maneuver is performed by hyperflexion and abduction of the maternal hips, flattening the lumbar spine, and rotating the pelvis to increase the anterior-posterior outlet diameter.
Suprapubic pressure is applied in a vector chosen to anteriorly rotate the anterior fetal shoulder and dislodge the shoulder from the symphysis.
Other measures in combination are chosen for the specific clinical situations based on clinician experience. There is no “right order” in which the maneuvers described below should be performed, and maneuvers can and should be used more than once, as needed.
Delivery of the posterior arm: By grasping the posterior hand, the posterior arm can be flexed and swept across the fetal chest, delivered first, thereby creating more room for the anterior shoulder. If the entire posterior arm cannot be delivered, an attempt at delivering the posterior shoulder by gentle upward traction on the fetal head can be performed.
Episiotomy: Incision of the perineum provides additional room and should be considered if it might facilitate delivery or additional maneuvering.
Rubin maneuver: The anterior fetal shoulder is rotated obliquely with a vaginal hand. This maneuver may also be performed in a posterior manner.
Wood corkscrew: The posterior shoulder is rotated over 180 degrees with a vaginal hand to assist delivery of the shoulders.
Gaskin maneuver: Facilitated in a patient without regional anesthesia, she is turned over on “all fours,” inverting the anterior and posterior shoulders.
Delivery that does not occur following the above maneuvers may require some of the more invasive and traumatic procedures noted below for the sake of fetal viability.
Management of neonatal clavicular fracture: Palpate the clavicles and apply outward pressure with the thumb to avoid lung or subclavian artery injury.
In extreme cases, the Zavanelli maneuver (in which the fetal head is flexed and pushed back up into the uterus as preparations for emergent cesarean section are made) or symphysiotomy (performed by laterally displacing the urethra using the index and middle fingers placed against the posterior aspect of the symphysis and incising the cartilaginous portion of the symphysis) could be performed.