Glucose challenge test: Screening threshold for gestational diabetes mellitus and associated outcomes

Objective. To examine whether women with an 1-hour 50-g glucose challenge test (GCT) for gestational diabetes mellitus (GDM) between 120 and 140 mg/dL and ≥140 mg/dL are at risk of perinatal complications.

Study design. A retrospective cohort study of women with singleton pregnancies screened for GDM between 1988 and 2001 with a 1-hour 50-g GCT. Values of GCT were stratified into four subgroups: <120, 120–129, 130–139, and ≥140 mg/dL. Perinatal outcomes were compared using the Chi-square test and multivariable logistic regression analysis.

Results. There were 13 901 women meeting the study criteria. Compared to women with a GCT of <120 mg/dL, women with a GCT of 130–139 mg/dL and ≥140 mg/dL were more likely to have preeclampsia and operative vaginal or cesarean deliveries. Neonates born to women with a GCT of 130–139 mg/dL also had higher odds of having a 5-minute Apgar score <7 (odds ratio (OR) = 1.51, 95% confidence interval (CI) 1.01–2.29), shoulder dystocia (OR = 2.02, 95% CI 1.16–2.55), birth trauma (OR = 1.47, 95% CI 1.06–2.02), and composite morbidity (OR = 1.25, 95% CI 1.03–1.51). Women with a GCT of ≥140 mg/dL had higher odds of macrosomia (OR = 1.32, 95% CI 1.13–1.54) and shoulder dystocia (OR = 1.68, 95% CI 1.11–2.55).

Conclusion. Women with GCT results of 130–139 mg/dL appear to be at increased risk for perinatal morbidity. Thus, utilizing a diagnostic test in women with a GCT above 130 mg/dL should be considered.