Shoulder dystocia

This occurs when there is an inability to deliver the shoulder after the head has been delivered.

• shoulder dystocia occurs when either the anterior, or less commonly the posterior, fetal shoulder impacts on the maternal symphysis, or sacral promontory, respectively
  • is a wide variation in the reported incidence of shoulder dystocia. Studies involving the largest number of vaginal deliveries (34 800 to 267 228) report incidences between 0.58% and 0.70%
  • can be significant perinatal morbidity and mortality associated with the condition, even when it is managed appropriately
    • maternal morbidity is increased, particularly the incidence of postpartum haemorrhage (11%) as well as third and fourth-degree perineal tears (3.8%). Their incidences remain unchanged by the number or type of manoeuvres required to effect delivery
    • brachial plexus injury (BPI) is one of the most important fetal complications of shoulder dystocia, complicating 2.3% to 16% of such deliveries
      • most cases of BPI resolve without permanent disability, with fewer than 10% resulting in permanent neurological dysfunction. In the UK and Ireland, the incidence of BPI was 0.43 per 1000 live births
        • however, this may be an underestimate as the data were collected by paediatricians, and some babies with early resolution of their BPI might have been missed
        • there is evidence to suggest that where shoulder dystocia occurs, larger infants are more likely to suffer a permanent BPI after shoulder dystocia (1)
• other reported fetal injuries associated with shoulder dystocia include fractures of the humerus and clavicle, pneumothoraces and hypoxic brain damage

This condition can be associated with:

• a large fetus - any cause of macrosomia increases the risk - in diabetics the fetal head may be of normal size but the body is disproportionately large and the shoulders fail to enter the pelvis as the head is delivered;
• post-mature fetus;
• short cord;
• rotational forceps delivery - this may occur because there is some degree of disproportion and the fetal head has failed to pass the pelvic outlet

Management:

• requires immediate expert intervention
• an obstetrician should be urgently summoned to the delivery room. This is an obstetric emergency that requires prompt action by a skilled practitioner.
• the mother is placed in lithotomy with her buttocks supported on a pillow over the edge of the bed. A large episiotomy is made.
• an assistant firmly applies suprapubic pressure directing the fetal head towards the floor. If delivery has still to be made then check that the anterior shoulder is under the symphysis. If not then an attempt may be made to rotate the anterior shoulder under this point (the point where the diameter of the outlet is widest) before repeating traction. If this is not possible then a rotation of the fetus through 180 degrees may be attempted so that the previously posterior shoulder now lies anteriorly.

Reference:

• RCOG (March 2012). Green Top Guideline (number 42) - Shoulder Dystocia