Shoulder Dystocia and Erb’s Palsy. One of the most serious complications of vaginal delivery in macrosomic babies is shoulder dystocia which is associated with birth trauma. Newborns with a birth weight of 4,500 g or morecarry a 6 times higher risk of birth trauma [17] , and the risk of brachial plexus injury is approximately 20 times higher when the birth weight is above 4,500 g [18] .