Clinical significance of a false positive glucose challenge test in patients with a high body mass index.

Objective: To determine if there is an increased maternal or neonatal morbidity in overweight and obese patients with a false positive glucose challenge test (GCT).

Methods: Patients with a body mass index (BMI) ≥25.0 at registration were included in this prospective 36-month study. The study cohort consisted of patients with a false positive (FP) GCT, with two comparison cohorts: those with a (1) screen negative (SN) GCT result and (2) true positive (TP) GCT result. Risks were reported as odd ratios with 95% confidence intervals, with a P<0.05 considered as significant.

Results: There were 60 patients in the FP cohort, 106 in the SN cohort, and 64 in the TP cohort. When the BMI of the FP cohort was compared with either the SN cohort or TP cohort, differences were non-significant (SN 32.3 vs. FP 33.3 kg/m2, P=0.067) and (FP 33.3 vs. TP 34.4 kg/m2, P=0.303). When comparing the FP cohort to the SN cohort, patients in the FP group had significantly more gestational hypertension and pre-eclampsia. There was a trend towards delivering large for gestational weight infants and an infant ≥4000 g in the FP cohort, but this fell short of reaching statistical significance. When comparing the FP to TP cohorts, rates of gestational hypertension, pre-eclampsia, and infants ≥4000 g were similar; however, neonatal morbidity was increased in the TP group.

Conclusions: Overweight and obese patients with a FP glucose challenge screen are more likely to have adverse maternal outcomes. Neonatal morbidity was not increased.