INFANT OF THE DIABETIC MOTHER - CORRELATION OF INCREASED CORD C-PEPTIDE LEVELS WITH MACROSOMIA AND HYPOGLYCEMIA

C peptide is secreted by pancreatic beta cells in amounts equimolar with insulin, and its levels provide a direct indication of endogenous fetal levels of insulin despite the presence of maternal insulin antibodies. To determine the presence of hyperinsulinemia and its relation to the development of complications in infants of diabetic mothers, we measured cord serum levels of C peptide in 79 infants of diabetic mothers and 62 infants of nondiabetic mothers. Infants of diabetic mothers had higher cord levels of C peptide, which were significantly associated with neonatal hypoglycemia and macrosomia (P<0.001) but not with hyaline-membrane disease. Cord levels of C peptide in infants of diabetic mothers were elevated at the earliest gestational age studied (<34 weeks) and were directly related to the severity of maternal diabetes, as assessed by the White classification. We conclude that hyperinsulinemia is present in infants of diabetic mothers and that it is related to some major complications in such infants. (N Engl J Med 301:859–862, 1979) MACROSOMIA, postnatal hypoglycemia and hyaline-membrane disease are three major complications that occur in infants of diabetic mothers. These complications may be related to the hyperinsulinemic state thought to be present in the fetuses of diabetic women.1 Indirect evidence of hyper-insulinism includes beta-cell hyperplasia and increased pancreatic insulin in fetuses of diabetic women2 and an increased rate of glucose disposal in newborn infants of diabetic mothers.3 Direct demonstration of hyperinsulinemia in infants of diabetic mothers has not been feasible because of interference in the immunoassay of insulin caused by the transplacental passage of maternal insulin antibodies generated by exogenous insulin therapy. © 1979, Massachusetts Medical Society. All rights reserved.