Clinical Outcomes of Pregnancies Complicated by Mild Gestational Diabetes Mellitus Differ by Combinations of Abnormal Oral Glucose Tolerance Test Values

OBJECTIVE: To examine the association between levels of hyperglycemia, determined by each prenatal oral glucose tolerance test (OGTT) value (fasting, 1 and 2 h), and maternal and perinatal outcomes and to determine whether the risk for these outcomes differs for women whose value(s) equaled or exceeded the thresholds for gestational diabetes mellitus (GDM) established by the International Association of Diabetes in Pregnancy Study Groups (IADPSG). RESEARCH DESIGN AND METHODS: This article discusses a retrospective study of 8,711 women, delivering at ≥ 20 weeks' gestation, who had a prenatal 2-h 75-g OGTT without a prior 50-g challenge and were not treated with insulin, glyburide, diet, and/or exercise during pregnancy. Associations between adverse outcomes and elevated OGTT values are reported. RESULTS: After excluding treated women, 19.4% of the remaining women had IADPSG-defined GDM. Continuous fasting, 1- and 2-h OGTT measures, and GDM (yes/no) were significantly associated with most adverse outcomes. However, the magnitude and significance of risk for these outcomes differed by various combinations of abnormal glucose values. Women with normal fasting and elevated postload values were at higher risk for preterm delivery, gestational hypertension, and having an infant with hyperbilirubinema, whereas women with elevated fasting and normal postload values were at higher risk of having a large-for-gestational-age infant, compared with women without GDM. CONCLUSIONS: Risks for different adverse outcomes vary depending on which single or combined IADPSG-defined OGTT thresholds are equaled or exceeded. Prospective studies are needed to determine whether changing pre- and postprandial glucose targets during pregnancy will more uniformly reduce adverse outcomes.