Comparing Glucose Challenge Test Screening Thresholds in Obese and Overweight Gravidas

Given the paucity of contemporary data examining glucose challenge test (GCT), thresholds for gestational diabetes (GDM) screening in obese and overweight women, we sought to compare the sensitivity and testing characteristics of different screen positive GCT cut-offs in women with a prepregnancy body mass index (BMI) ≥ 25 kg/m².

This is a retrospective cohort study of obese and overweight women with singleton pregnancies who underwent GCT between 24 and 29^6/7 weeks and had a value between 130 and 199 mg/dL necessitating a 3-hour glucose tolerance test (GTT). Exclusion criteria were pregestational diabetes mellitus, multigestation, use of diabetes medications, and bariatric surgery.

Between August 2015 and January 2016, 19% (n = 496) of women with a BMI ≥ 25 kg/m² required a GTT to test for GDM, 27.8% (n = 138) of whom were diagnosed with GDM. Mean age was 30 years, mean BMI = 31.6 kg/m², and 30.4% were Hispanic. The 130 mg/dL threshold compared with 140 mg/dL was more sensitive (absolute increase: 11.3%, 95% confidence interval [CI]: 6.7-17%), but less specific (absolute decrease: 6.4%, 95% CI: 5.5-7.5%).

Shared decision making should be used to determine GCT cut-offs as some patients may prefer to undergo a GTT rather than miss a diagnosis of GDM.