Despite recent emphasis upon improved metabolic control during early diabetic pregnancy, the offspring of insulin-dependent diabetic women continue to have a 2- to 4-fold increased risk of congenital malformations. We recently evaluated the affected offspring of 4 insulin-dependent diabetic women. All had abnormal ears in association with vertebral defects. Our analysis of the structural defects of these infants and a review of the literature suggest that the pathogenesis of some cases of the diabetic embryopathy may involve a primary insult to developing somite mesoderm and associated cephalic neural crest cells.