Shoulder dystocia occurs when one shoulder of the fetus lodges against a pregnant woman’s pubic bone or sacrum during deliver, and the baby is therefore caught in the birth canal.
In shoulder dystocia, the head of the fetus delivers but the shoulder becomes lodged against the mother’s pubic bone or sacrum. Consequently, the head pulls back slightly into the vagina. The baby cannot breathe because the birth canal puts pressure on the chest and umbilical cord. As a result, oxygen levels in the baby’s blood decrease, and there is a risk of injury or death.
Shoulder dystocia is not common, but it is more common when any of the following is present:
Difficult, long, or rapid labor
Delivery assisted by a vacuum device or forceps, because the fetus’s head has not fully moved down (descended) in the pelvis
Obesity
Prior delivery of a baby with shoulder dystocia
When shoulder dystocia occurs, the doctor quickly tries various techniques to free the shoulder so that the baby can be delivered vaginally. An episiotomy (an incision that widens the opening of the vagina) may be done to help with delivery.
If these techniques are unsuccessful, the baby may be pushed back into the vagina and delivered by cesarean delivery.
Shoulder dystocia increases the risk of problems and of death in the newborn. The newborn's bones may be broken during delivery, and the brachial plexus (the network of nerves that sends signals from the spinal cord to the shoulders, arms, and hands) may be injured. The pregnant woman is also more likely to have problems such as
Excessive bleeding at delivery (postpartum hemorrhage)
Tears in the area between the vaginal opening and the anus
Injury of muscles in the genital area and nerves in the groin
Separation of the pubic bones.
