Shoulder dystocia occurs when there is a mechanical obstruction of the anterior fetal shoulder during the birthing process after the head is delivered. The basis of any litigation related to shoulder dystocia is – 1) Did they identify risk factors, and 2) Did they respond appropriately? In Part 1 of this series, we discussed the interventions utilized to resolve a shoulder dystocia. In Part 2 of this series, we discussed some of the risk factors associated with an increased incidence of shoulder dystocia. It is imperative that healthcare providers identify any potential risk factors and prepare for complications in those deemed at risk. In Part 3, we will discuss brachial plexus injuries and neonatal hypoxia in the newborn as a consequence of delivery complicated by shoulder dystocia.
The brachial plexus is a group of nerves that come from the spinal cord in the neck and travel down the arm. They control the muscles of the shoulder, elbow, wrist and hand as well as sensation in the arm. Stretching of these nerves during a difficult delivery can lead to temporary or permanent damage. It is knot known how much traction is required to damage the nerves in this area. An injury to the brachial plexus can occur during a vaginal delivery or during a cesarean section if too much traction is applied to the fetal head and neck.
Erb’s palsy involves the 5th and 6th cervical nerves. It is the most common brachial plexus injury occurring in 0.9 to 2.6 per 1,000 live births. An injury in this area cases weakness of the upper arm. Adduction and internal rotation of the arm with flexion of fingers are presenting symptoms. The injury significantly impact 0.5-5 in 10,000 live births. Klumpke’s palsy involves the 8th cervical and 1st thoracic nerves. It causes paralysis of the hand muscles, absent grasp reflex, and sensory impairment along the ulnar side of the forearm and arm. It is much less common than Erb’s palsy, but generally does not recover without intervention. 90% of brachial plexus injuries resolve spontaneously by 6 months of age. If the stretched nerve does not resolve spontaneously or with physical therapy, the child may require surgery to graft a donor nerve, or in the case of avulsion, when the nerve is torn from the spinal cord, a nerve from another muscle may have to be surgically transferred as a donor.
In the fetus with a reassuring heart rate tracing prior to birth, acidosis quickly develops after 5 minutes if the head is delivered and the fetal body remains trapped within the birth canal. The umbilical cord, which provides oxygenated blood and removed carbon dioxide – an acid – from the baby’s blood, is compressed during this time and the baby is essentially “holding its breath” until the body is delivered. There is no oxygen flowing to the baby and the carbon dioxide begins to build up. The healthcare providers should anticipate a depressed newborn in need of resuscitation particularly if there is a prolonged dystocia more than 2.5 minutes in length. If the interval from delivery of the head to delivery of the body is more than 5 minutes, the baby may develop irreversible hypoxic brain damage. In a fetus who goes into the delivery already compromised, they have a much lower tolerance for lack of oxygenation issues during the birthing process.
Shoulder dystocia is neither preventable or predictable, but can be anticipated in women with multiple risk factors. It is the duty of healthcare providers to ensure that they identify women at risk for this complication and have appropriate resources and staff in attendance at the delivery to institute McRoberts Maneuvers and assist with other delivery maneuvers as needed as well as providing advanced resuscitation to a compromised newborn if necessary.