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 less than 0.001), and maternal and cord blood levels were highly correlated in the diabetic group (r = 0.61, P less than 0.001). Cord serum C-peptide and glycosylated hemoglobin levels tended to be associated (r = 0.43, P less than 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 less than 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 greater than 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.