Gestational diabetes mellitus (GDM) is associated with adverse maternal and perinatal outcomes. Growing evidence suggests mild maternal hyperglycemia is also associated with poor outcomes. Our objective was to assess the association between an abnormal 1-hour 50-gram glucose challenge test (GCT) followed by a normal 3-hour 100-gram glucose tolerance test (GTT) on fetal macrosomia and other adverse outcomes.
Prospective and retrospective studies which the maternal and perinatal impact of an abnormal 50-gram 1-hour glucose challenge test (GCT) followed by a normal 3-hour, 100-g glucose tolerance test (study group) in comparison to patients with a normal GCT (comparison group) were identified using computerized databases. Data were extracted and quantitative analyses were performed.
We identified 20 studies comprising 10,001 patients with a normal 3 hour GTT after an abnormal 1-hour GCT (study group) and 58,392 patients with a normal GCT. Patients in the study group had an increased risk of macrosomia (RR 1.71, CI 1.50-1.95), shoulder dystocia (RR 1.51, 95% CI 1.09-2.09), cesarean delivery (RR 1.27, 95% CI 1.19-1.36), and pre-eclampsia (RR 1.52, 95% CI 1.03-2.23). Neonatal birth weight was significantly increased in the study group. The predictive interval for macrosomia indicates that in 95% of future studies, the true effect will range from 1.15-2.5. NICU admission, low Apgar score, hypoglycemia, and respiratory morbidity were not significantly different between groups.
Even in the absence of GDM, patients that fail the GCT test but have a normal GTT are at increased risk of maternal and neonatal morbidity including macrosomia and cesarean delivery.