Changing Glucose Tolerance during Pregnancy—Implications for Diagnosis of Gestational Diabetes Mellitus (GDM)

Abstract

Background: ADA recommends testing for GDM at 24-28 weeks gestation. This recommendation is based on the assumption that glucose tolerance worsens during pregnancy and, therefore, testing earlier in pregnancy will miss many cases that develop only later. We tested this assumption in the LIFE-Moms consortium. Methods: LIFE-Moms was a consortium of randomized clinical trials of lifestyle interventions aimed at limiting gestational weight gain compared with standard care in 1,150 pregnant women with BMI ≥25 kg/m2 recruited from different racial/ethnic groups in the U.S. Women with known or probable diabetes preceding this pregnancy were excluded. As previously reported, the lifestyle interventions modestly reduced excessive gestational weight gain (the primary outcome) but had no significant effect on the prevalence of GDM at 24-31 weeks. We report here results of 75 g 2-hour OGTTs performed sequentially during pregnancy in a subset of 296 women tested at <16 weeks (mean 12.6 weeks) gestation and again at 24-31 weeks. Tests were interpreted by the International Association of Diabetes in Pregnancy Study Groups (IADPSG) criteria. Results: Plasma or serum glucose declined from the early to later tests by a mean of 2.5 mg/dl (fasting), 10.9 mg/dl (1-hr), and 9.3 mg/dl (2-hr), each p<0.0001. The prevalence of GDM by IADPSG criteria declined from 20% at <16 weeks gestation to 15% at 24-31 weeks (p=0.04). Only 9% of women without GDM at <16 weeks gestation developed it by 24-31 weeks, whereas 65% of those meeting GDM criteria at <16 weeks gestation did not meet GDM criteria at follow-up. None of the changes in glucose or GDM prevalence differed significantly by treatment group. Conclusions: In pregnant women with BMI ≥25 kg/m2 who are otherwise healthy, glucose tolerance improves on average rather than deteriorates during gestation. Testing for GDM early in pregnancy is needed to understand pregnancy effects on glycemia and the clinical implications of earlier detection of GDM. Disclosure W.C. Knowler: None. K. Drews: None. L. Redman: None. K.J. Joshipura: None. S. Arteaga: None. X. Pi-Sunyer: None. L. Van Horn: None. R.R. Wing: None. S. Klein: Stock/Shareholder; Self; Aspire Bariatrics. Consultant; Self; Pfizer Inc.. Research Support; Self; Merck & Co., Inc., Johnson & Johnson Services, Inc., REMD Biotherapeutics.