OBJECTIVE To evaluate retrospectively the glucose metabolism of women who gave birth to large babies.

RESEARCH DESIGN AND METHODS Within the first 3 days of postpartum, HbA_1c of the dense erythrocytes and glycated albumin were measured. The sample group was comprised of 59 women who gave birth to heavy-for-dates infants. Fifty-five women who had average-sized infants formed the control group. Both groups had normal results on screening for gestational diabetes mellitus (GDM) by 28 weeks of gestation. The dense erythrocyte fractionation was obtained by capillary centrifugation for measurement of stable HbA_1c.

RESULTS Mothers of heavy-for-dates infants had a significantly higher level of HbA_1c of the dense erythrocytes (mean ± SD; 5.86 ± 0.68 vs. 5.50 ± 0.70%, P = 0.015) and a higher maternal body mass index (BMI) (mean ± SD; 26.5 ±2.9 vs. 24.1 ±2.3 kg/m2, P < 0.00001) than control mothers. Differences in the occurrence of high levels of HbA_1c of the dense erythrocytes and maternal BMI were statistically significant (P < 0.01, P < 0.05) between the two groups, but no difference was noted in glycated albumin. There was no statistical correlation between high levels of HbA_1c of the dense erythrocytes and maternal obesity.

CONCLUSIONS High HbA_1c levels of the dense erythrocytes and maternal obesity are independent factors that affect fetal oversize. Heavy-for-dates infants may be a consequence of maternal hyperglycemia in late pregnancy. This maternal hyperglycemia was not detected by the routine screening test for GDM.