Erb's palsy: concepts of causation.

In the past, obstetric textbooks have stated (without evidence) that Erb's palsy is caused by the birth attendant. The mechanism cited is stated to be the application of excessive lateral traction placed on the fetal head and neck. Recent research findings refute this unproven theory. Findings include (1) only 50% of cases are associated with shoulder dystocia; (2) the 4.7-fold increase in the condition was associated with a precipitate second stage compared with one of normal length; and (3) the same injury rate with direct manipulation techniques (for resolving shoulder dystocia) was comparable to that of McRobert's position and/or suprapubic pressure. The overwhelming evidence indicts the propulsive nature of the stretching of the involved nerves over which the birth attendant has no control.