Diabetes Mellitus is known to be associated with certain HLA types. It is also known to cause malformation in infants of diabetic mothers. This study will examine the relationship between HLA "markers" for diabetes and malformations. The pilot study undertaken last year demonstrated that diabetic women with malformed offspring have an extremely high rate of DR3 and DR4 HLA types. Because of this interesting finding, the major part of the study has started. HLA typing is now being performed on diabetic women with normal offspring to determine whether the HLA markers are equally common in that group. If they are not, it will indicate that HLA type may be a useful indicator for risk of producing malformed children.