Dystocia of shoulder

Shoulder dystocia (SD) refers to the failure of the shoulder to be delivered during childbirth and the need for extra-obstetric maneuvers to facilitate their passage after normal smooth gentle downward traction has failed. Dystocia literally means difficult labor.

Epidemiology

The incidence of shoulder dystocia ranges from 0.6% to 3% among cephalic vaginal deliveries.

Clinical presentation

Shoulder dystocia is, in practice, a clinical diagnosis.  The fetal head is applied firmly to the vulva or it may retract after delivery. The characteristic hallmark of clinical turtle sign ( which should not be confused with turtle sign on ultrasound or turtle back sign ) can often be seen.

Pathology

Shoulder dystocia results from impaction of the anterior fetal shoulder or less commonly the posterior shoulder on the maternal symphysis pubis or sacral promontory, so the shoulder fails to pass spontaneously. It is a terrifying unpredictable emergency for all healthcare providers worldwide.

Risk factors

• advanced maternal age
• abnormal pelvic anatomy
• short stature
• maternal diabetes
• post dates
• macrosomia
• prolonged first or second stage of labor
• improper maneuver (fundal pressure)
• oxytocin augmentation

Treatment and prognosis

Complications

Maternal

• uterine rupture
• postpartum hemorrhage
• symphysis pubis diastasis
• transient femoral neuropathy
• recto-vaginal fistula

Fetal

• birth trauma
  • hypoxic-ischemic encephalopathy
  • fetal death
  • brachial plexus injury (Erb palsy)
  • clavicle and/or humeral fractures   

Practical points

Prepartum ultrasound estimation of fetal size and weight may have some value in predicting the probability of difficult deliveries including shoulder dystocia, however many of the cases of shoulder dystocia occur with normally sized babies , and some large babies are delivered easily.