Umbilical Cord Glycosylated Hemoglobin in Infants of Diabetic Mothers: Relationships to Neonatal Hypoglycemia, Macrosomia, and Cord Serum C-Peptide

Relationships of neonatal glycemia and birthweight to antecedent fetal glycemia and insulinemia have been examined in the offspring of 63 insulin-dependent diabetic and 29 nondiabetic mothers. Glycosylated hemoglobin levels in maternal and cord blood were measured by the thiobarbituric acid (TBA) colorimetric technique to estimate antecedent fetal and maternal glycemia; cord serum C-peptide was assayed to estimate fetal insulinemia. Glycosylated hemoglobin levels were significantly elevated in the diabetic mothers and their offspring as compared with controls (P < 0.001), and maternal and cord blood levels were highly correlated in the diabetic group (r = 0.61, P < 0.001). Cord serum C-peptide and glycosylated hemoglobin levels tended to be associated (r = 0.43, P < 0.10). Hypoglycemic infants of diabetic mothers (IDM) had significantly higher glycosylated hemoglobin levels (A₄₄₃ nm/10 mg hemoglobin hemolysate) in cord blood (0.173 ± 0.009) than did IDM without hypoglycemia (0.153 ± 0.005, P < 0.01). Macrosomic and nonmacrosomic IDM, on the other hand, did not differ as to their glycosylated hemoglobin levels (0.162 ± 0.005 versus 0.161 ± 0.006, respectively). The occurrence of hypoglycemia was not associated with that of macrosomia (X² = 0.24, P > 0.10). These data strongly suggest that neonatal hypoglycemia is the result of maternal hyperglycemia in pregnancy and consequent fetal hyperglycemia and hyperinsulinemia. However, maternal hyperglycemia in late pregnancy may not be a sufficient explanation for the development of macrosomia in IDM.