Shoulder dystocia

1. Big picture

Shoulder dystocia is an unpredictable obstetric emergency in which the fetal head is born, but the shoulders fail to deliver with normal gentle traction because the anterior shoulder becomes impacted behind the maternal pubic symphysis, or less commonly the posterior shoulder becomes impacted on the sacral promontory.

The key exam sentence:

Shoulder dystocia = head delivered, body not delivered → call for help → stop traction/fundal pressure → McRoberts + suprapubic pressure → internal manoeuvres/posterior arm → last-resort procedures.

It is dangerous because once the head is born, the umbilical cord may be compressed, so prolonged delay can cause fetal hypoxia, brachial plexus injury, or death.

Head delivered
↓
Shoulders stuck
↓
Cord compression + chest cannot expand
↓
Fetal hypoxia risk increases with time
↓
Rapid, organized manoeuvres are needed