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

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).

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.

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.

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