II.

Longitudinal changes in glycosylated hemoglobin concentration (GlyHb) and glycosylated serum protein concentration (GSP) in both normal pregnancy and pregnancy complicated by gestational diabetes were determined using affinity chromatography, a method in which nonenzymatically glycosylated proteins are specifically measured. At 7-10 wk gestation, GlyHb in women who developed diabetes (N = 21) was higher than GlyHb in normal women (N = 49) (6.7 +/- 0.2% versus 5.7 +/- 0.2%, respectively, P less than 0.001) and remained elevated throughout gestation. In normal pregnancy, GlyHb decreased to a nadir at 23-26 wk and returned to baseline concentration by 31-34 wk. In gestational diabetes, there was an initial increase in GlyHb to 7.1 +/- 0.5% at 11-14 wk followed by a steady decrease. At 7-10 wk, GSP in women who developed diabetes was not elevated compared with normal concentration, although at 11-14 wk there was significant difference between the two groups (P less than 0.02). In normal women, GSP remained constant throughout gestation. In gestational diabetes, GSP decreased to early pregnancy values (P less than 0.02). Glycosylated blood proteins were elevated in early gestation in women who developed gestational diabetes and may have predictive value in identifying women who will develop diabetes in pregnancy.

Previous studies suggested that the assessment of hemoglobin A1 (HbA1) concentration was a poor indicator of diabetes in pregnancy. However, HbA1 was measured by ion exchange chromatography, which is subject to spurious alterations. To reevaluate the use of glycosylated hemoglobin concentration (GlyHb) as an indicator of gestational diabetes, 64 women at 10 to 15 weeks' gestation were studied by measuring GlyHb by a specific affinity chromatography assay, and blood glucose concentration was determined one hour post a 50-g oral glucose load. Gestational diabetes developed in 15 women in whom GlyHb (7.4 +/- 0.2%) was greater than in normal pregnant women (5.7 +/- 0.1%, P less than .001). If a GlyHb of 6.3% were chosen as the threshold for diagnostic evaluation for diabetes, only 6.7% of the gestational diabetics would have missed diagnosis. Of normal women, 14.2% would have been subjected to glucose tolerance test. GlyHb elevation was associated with the birth of infants large for gestational age. The assessment of GlyHb by affinity chromatography between 10 and 15 weeks' gestation may be a sensitive predictor of patients who will develop gestational diabetes.

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