First Trimester Maternal Glycated Hemoglobin and Sex Hormone-Binding Globulin Do Not Predict Third Trimester Glucose Intolerance of Pregnancy

Early pregnancy prediction of third trimester glucose intolerance may identify a population of women whose trajectory toward gestational diabetes mellitus (GDM) is modifiable. We assessed whether first trimester glycated hemoglobin (HbA1c) and sex hormone-binding globulin (SHBG), markers of insulin resistance, predicted third trimester glucose intolerance. Nondiabetic women with singleton pregnancies enrolled in a prospective observational study, 11 0/7 to 14 6/7 weeks. At enrollment, maternal characteristics, medical history, and blood samples were collected for HbA1c and SHBG. Two-step GDM screening was performed, 22 0/7 to 33 6/7 weeks. A 50 g oral glucose tolerance test >= 130 mg/dL defined screen positive, or glucose intolerance. Carpenter-Coustan criteria diagnosed GDM. Means HbA1c and SHBG were compared between glucose-intolerant versus normoglycemic women, and GDM versus no GDM women. We report unadjusted and adjusted odds ratios (OR; 95% confidence interval [CI]) of regression analyses. Adjusted models include race, enrollment body mass index, and history of GDM. Among 250 women, 29% were glucose intolerant and 6% had GDM. Among glucose-intolerant women, HbA1c was higher (5.3 +/- 0.3 vs. 5.1 +/- 0.3, P = .01) and associated with glucose intolerance in unadjusted, but not adjusted, models (OR: 2.9, 95% CI: 1.2-7.1; adjusted odds ratio [aOR]: 2.0, 95% CI: 0.7-5.4). Among GDM women, HbA1c was higher (5.4 +/- 0.4 vs 5.2 +/- 0.3, P = .002) and SHBG was lower (228 +/- 72 vs 288 +/- 93 mmol/L, P = .02). The HbA1c predicted GDM in unadjusted (OR: 13.2, 95% CI: 2.6-68.0) but not adjusted (aOR: 6.7, 95% CI: 0.8-55.2) models. Although metabolic alterations may well precede third trimester glucose intolerance, neither HbA1c of SHBG remained an independent predictor of glucose intolerance or GDM in adjusted models.