A difficult birth (see dystocia) in which the anterior or, less commonly, the posterior fetal shoulder impacts on the maternal symphysis or sacral promontory. It is an obstetric emergency and is diagnosed when the shoulders fail to deliver after the fetal head when gentle downward traction has failed. Additional obstetric manoeuvres (e.g. McRobert’s manoeuvre) are required to release the shoulders from below the pubic symphysis. It occurs in approximately 1% of vaginal births. There are well-recognized risk factors, such as diabetes, fetal macrosomia, and maternal obesity, but it is often difficult to predict. There can be a high perinatal mortality rate and morbidity associated with the condition, even when it is managed appropriately. The most common fetal injuries are to the brachial plexus, causing an Erb’s palsy or Klumpke’s paralysis, and hypoxic-ischaemic encephalopathy. Maternal morbidity is also increased, particularly postpartum haemorrhage and fourth-degree perineal tears (OASIS).
Subjects: Medicine and Health.