After delivery of the baby’s head, shoulder dystocia occurs when the baby’s anterior shoulder gets lodged or stuck behind the mother’s pubic bone. If this should occur, it makes it particularly difficult for the remainder of the baby to follow the head out of the vagina as it normally would under vaginal deliveries.
The most common and serious complication known following a shoulder dystocia delivery is brachial plexus injury. A brachial plexus injury occurs when the nerves in a baby’s neck are temporarily or permanently damaged. The nerves of the brachial plexus control the function of the arm and hand. If the upper part of the brachial plexus is injured, it is called Erb palsy, while injury to the lower nerves of the plexus is called Klumpke palsy. Both of these injuries can cause significant and permanent disability.
Fetal injuries incurred following shoulder dystocia
Twenty (20%) percent of babies will suffer some sort of injury in either temporary or permanent stature. The most common injury being damage to the brachial plexus nerves, fractured clavicles, fractured humeri, contusions and lacerations, and birth asphyxia (suffocation).
There are two major types of brachial plexus injury as stated above (Erb palsy and Klumpke palsy).
The upper trunk of the brachial plexus located in nerve innervations at C5 through C7 which affects the muscles of the upper arm and causes abnormal positioning of the scapula called “winging.”
The lower trunk lesions from nerve innervations at C7, C8 and T1 causes the elbow to become flexed and the forearm supinated (facing in an upward, open position) with a characteristic claw-like deformity of the hand. Sensation in the palm of the hand is decreased.
Those patients with Erb Palsy have a better prognosis than those with lower brachial plexus injuries (Klumpke Palsy). Approximately 90-95% those affected by Erb Palsy totally resolve and only 60% of those with Klumpke Palsy do not. Those brachial plexus injuries associated with non-shoulder dystocia deliveries occur more often than those occurring following a shoulder dystocia delivery.