'Minor hemoglobins': an alternative approach for evaluating glucose control in pregnancy.

'Minor hemoglobins' (Hb AI) were measured in 178 women during pregnancy and immediately postpartum by a thiobarbituric acid spectrophotometric method. The patients were classified according to an oral glucose tolerance test (GTT) and an assessment of risk factors for diabetes in normal (n = 75), probably normal (n = 72) and chemical diabetics (n = 26). 5 pregnant insulin-dependent diabetics were also studied. Hb AI was unchanged during the second and third trimesters of pregnancy and immediately postpartum (less than 6 days) in women with normal glucose tolerance. Moreover, no difference of Hb AI level was found when compared with a separate group of nonpregnant individuals (n = 15). Chemical diabetics had significantly higher mean third trimester and postpartum Hb AI than normals (p less than 0.001). The highest Hb AI levels during pregnancy were found in the insulin-dependent diabetics, although these were lower compared to a separate group of nonpregnant insulin-dependent diabetics (n = 10; p less than 0.05). During pregnancy, a significant correlation was found between Hb AI and the 2-hour value of the GTT (p less than 0.001). A positive correlation was also found between third trimester maternal Hb AI and infant birth weight (p less than 0.001). Hb AI may complement other parameters in evaluating maternal glucose tolerance during pregnancy.