Obstetrical brachial plexus palsy is a disorder of the peripheral nervous system and occurs in as many as 0.4% of infants born. It is associated with shoulder dystocia, use of mechanical extraction, and macrosomia; it occurs more frequently in infants born by vaginal delivery. The unilateral injury to the brachial plexus complex occurs during the delivery phase as lateral traction is applied to the head to permit shoulder clearance. The infant typically presents in the delivery room with decreased active movements of the affected arm and asymmetrical primitive reflex responses. The severity of nerve involvement can range from a stretch injury to complete avulsion. While full recovery is possible, prognosis is variable and up to 35% of children may have some degree of life-long functional impairment of the affected limb.