An attempt to study macrosomia and carbohydrate metabolism was made by determination of glycated hemoglobin A1c and by the oral glucose tolerance test (OGTT) in early puerperium. We studied 76 women who gave birth to large babies greater than or equal to 4.5 kg, 74 women whose babies were 3-4 kg as controls, and 36 type II diabetics. The median of HbA1c concentration in the diabetics (8.06%) was significantly higher than in the controls (6.49%), and the large babies' mothers (6.48%), P less than 0.001. No significant difference was found between HbA1c or glucose intolerance in mothers of large babies and mothers with average size babies. HbA1c showed an association with glucose levels in the diabetics and controls, P less than 0.001, but not in the large baby group. Mothers of large babies were as old and obese as the diabetics. We speculate that the relationship of postpartum GTT, HbA1c and gestational diabetes is unwarranted.