Intrauterine shoulder weakness and obstetric brachial plexus palsy.

Obstetrical brachial plexus injury occurs when the forces preventing the stretch of the brachial plexus are overcome by the forces stretching it. This report describes an 8-day-old male delivered by uncomplicated cesarean section with right obstetrical brachial plexus palsy and congenital arm atrophy. The patient had a history of decreased right arm movement detected by fetal ultrasound at 18 to 20 weeks of gestation. The purpose of this article is to report that stretching of brachial plexus at birth sufficient to produce a plexus injury may occur in a patient with a vulnerable plexus even in the absence of traction during delivery.