Pregnancy outcomes associated with an abnormal 50-g glucose screen during pregnancy: a systematic review and Meta-analysis

Objective: To assess the association between an abnormal 1-h 50-g glucose challenge test (GCT) followed by a normal 3-h 100-g glucose tolerance test (GTT) on fetal macrosomia and other adverse outcomes. Data sources: MEDLINE, Cochrane, clinicaltrials.gov, and Google Scholar were searched from inception to March 2019. Methods of study selection: Any studies reporting adverse perinatal and/or maternal outcomes in women with an abnormal 50-g 1-h glucose challenge test (GCT) followed by a normal 3-h, 100-g glucose tolerance test (GTT) were included. Studies were critically appraised by three independent reviewers. Outcomes included fetal macrosomia, cesarean delivery, preeclampsia, birth weight, neonatal hypoglycemia, shoulder dystocia, NICU admission, respiratory morbidity, and low Apgar score. A random-effects model was employed to calculate pooled odds ratios (OR) for each outcome with their 95% confidence intervals (CI) and 95% predictive intervals (PI). Tabulation, integration, and results: We identified 30 studies comprising 18,067 patients with a normal 3-h GTT after an abnormal 1-h GCT (study group) and 117,091 patients with a normal 1-h, 50-g GCT (comparison group). Patients in the study group had an increased risk of macrosomia (OR 1.68, 95% CI 1.48–1.91, 27 studies, 132,027 patients), cesarean delivery (OR 1.39, 95% CI 1.30–1.48, 24 studies, 128,495 women), preeclampsia (OR 1.48, 95% CI 1.15–1.91, 17 studies, 110,930 patients), hypoglycemia (OR 1.43, CI 1.07–1.91) and shoulder dystocia (OR 1.52, 95% CI 1.09–2.12, 9 studies, 41,229 patients). Neonatal birth weight was significantly higher in the study group. The incidence of NICU admission, low Apgar score, and respiratory morbidity was similar in the two groups. Controlling for body mass index and 1-h glucose screen cut off did not alter these results. Conclusion: Even in the absence of gestational diabetes, patients who fail the GCT test are at mildly increased risk of maternal and neonatal morbidity including macrosomia, cesarean delivery, preeclampsia, and shoulder dystocia.