Shoulder dystocia happens when a fetus is too large for the mother’s pelvis or when a fetus is in an abnormal position in relation to the mother’s pelvis. When this occurs, the infant’s head delivers, but one of the shoulders is caught.
Shoulder dystocia is a serious emergency requiring immediate intervention to free the shoulder and fully deliver the infant. While it is difficult to predict and prevent shoulder dystocia, certain factors help identify who is at risk.
Shoulder Dystocia Risk Factors
- Large fetus
- Maternal weight gain of more than 35 pounds during pregnancy
- Maternal obesity (having a BMI greater than 30 kg/m2)
- Diagnosis of diabetes mellitus before or during pregnancy
- Previous delivery complicated by a shoulder dystocia
- Rapid or prolonged second stage of labor
- Operative vaginal delivery
- Delivering after 40 weeks gestation
- Pregnant with two or more babies
Shoulder Dystocia Management
As soon as a shoulder dystocia is identified, special maneuvers are performed to reposition the mother and free the infant’s shoulder.
The McRoberts maneuver requires the mother to draw her legs in to her abdomen in a flexed position to widen the birth canal. Applying manual pressure in the suprapubic region (lower abdomen) may also successfully free the shoulder.
There are more invasive maneuvers a doctor can perform—including delivering the arm that is not stuck (known as delivery of the posterior arm), turning the baby, and then trying to deliver (known as Woods’ screw maneuver).
If a series of different maneuvers proves unsuccessful, the infant may be pushed back into the birth canal and rushed to the operating room for an emergency cesarean section. The delivering physician or midwife should not simply pull harder to deliver the baby, as this can result in serious permanent injury to the baby’s nerves.
Poor Outcomes Associated with Shoulder Dystocia
Complications of shoulder dystocia vary in severity. The most common injury associated with shoulder dystocia is injury to the brachial plexus nerves. These nerves control the function of the shoulder, arm, and hand.
A common brachial plexus injury that occurs with shoulder dystocia is known as Erb’s palsy. Permanent Erb’s palsy, or other brachial plexus injury, following a shoulder dystocia is usually the result of excessive pulling by the delivering doctor or midwife. Further, if the dystocia is prolonged, the infant is at risk of receiving inadequate oxygen and nutrients to the brain.