First trimester fasting hyperglycemia as a predictor for the development of gestational diabetes mellitus

Abstract

Objective: Screening for gestational diabetes mellitus (GDM) is usually done at 24-28 weeks of gestation. Our goal was to study the association between first trimester fasting plasma glucose level and GDM risk and to evaluate its efficacy as a screening test for GDM in comparison to a traditional risk factor, pregestational body mass index (BMI).

Study design: The charts of all patients who delivered in our hospital between June 2001 and June 2006 were reviewed. Only subjects with a singleton pregnancy and a recorded first trimester fasting glucose level and BMI were studied. Women with pregestational diabetes mellitus, fasting glucose level >105mg/dl or delivery at <24 weeks were excluded. Screening properties of both fasting glucose level and BMI were calculated and compared using receiver operator characteristic curves.

Results: GDM was diagnosed in 135 of the 4876 women included in this study. Fasting glucose cut-off levels of 80-85mg/dl yielded sensitivities of 75-55% and specificities of 52-75% for GDM prediction. BMI cut-off values of 25-28 had sensitivities of 60-40% and specificities of 72-86% for GDM prediction. Receiver operator curves for fasting glucose levels and BMI showed similar performance in predicting GDM (area under curve 0.72±0.023 vs. 0.74±0.021 (P=0.44)). There was approximately a 1.5-fold increase in the risk of developing GDM with each 5mg/dl increase in fasting glucose or 3.5kg/m² increase in BMI.

Conclusion: Higher first trimester fasting glucose levels, within the normoglycemic range, constitute an independent risk factor for the development of GDM among young pregnant women.