Despite improved prenatal care, infants of diabetic mothers (IDM) have an increased risk of congenital malformations. We report on an IDM with multiple congenital anomalies consistent with the polyasplenia complex with associated mesocardia and renal agenesis. The morphologic characteristics of these malformations are discussed. Special emphasis is given to the polyasplenia complex as an example of midline developmental field defect. The importance of maternal levels of hemoglobin A1c in relation to congenital malformations is addressed.