Background: It is unclear what diagnostic criteria for hyperglycemia should be applied in early pregnancy; some suggest applying criteria used outside of pregnancy, while others suggest applying gestational diabetes mellitus (GDM) criteria. Prior studies have reported inconsistent changes in glucose levels across pregnancy.

Methods: We recruited women with at least 1 risk factor for GDM. We performed 75-gram oral glucose tolerance tests on 40 non-pregnant (NP) women and serially on 71 pregnant women [completed visits: 71 at 10-14 (mean 12.8) weeks gestation (V1), 46 at 24-28 (mean 26.8) weeks gestation (V2), 32 at 6 weeks-6 months postpartum (V3)]. We tested for differences in glucose levels between the NP and pregnant women at V1, V2, and V3 using linear regression, with adjustment for age and family history of diabetes. We tested for longitudinal differences in glucose levels across pregnancy and postpartum (V1, V2, and V3) using mixed effects models.

Results: Fasting glucose was lower in pregnant compared to NP women by 5.0 mg/dl at V1 (P=0.01) and 5.7 mg/dl at V2 (P=0.01). Fasting glucose was lower by 2.8 mg/dl at both V1 and at V2 compared to postpartum values (V1 vs. V3, P=0.04; V2 vs. V3, P<0.05). Post-load glucose at V1 did not differ from V3 or NP women. At V2, 30 minutes and 1 hour post-load glucose levels were higher in comparison to both V3 and NP levels (30 minutes: V2 vs. V3 9.7 mg/dL P=0.02, V2 vs. NP 12.0 mg/dL P=0.04; 1 hour: V2 vs. V3 13.0 mg/dl P=0.04, V2 vs.NP 21.1 mg/dL P=0.02). Two-hour post-load glucose did not differ between V2 and NP or V3 levels (P>0.3 for all comparisons). There were no differences between V3 and NP glucose levels (P>0.1 for all comparisons).

Conclusion: We confirmed reduced fasting glucose in pregnant women, with stability from the late 1st trimester through the early 3rd trimester. In contrast, early post-load glucose values increased in late pregnancy. This implies that establishing pregnancy- and gestational age- specific diagnostic criteria for hyperglycemia is imperative.


M.A. Bochkur Dratver: None. K. James: None. J. Arenas: None. M. Cayford: None. M.J. Callahan: None. J.S. Tangren: None. S.N. Bernstein: None. M. Hivert: None. C.E. Powe: None.


National Institute of Diabetes and Digestive and Kidney Diseases (K23DK113218); Robert Wood Johnson Foundation; Eunice Kennedy Shriver National Institute of Child Health and Human Development (R01HD094150)

Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. More information is available at