The association between low 50g glucose challenge test result and fetal growth restriction

Objective: To determine whether a low-GCT result is predictive of low birthweight and to identify the lower GCT threshold for prediction of fetal growth restriction. Methods: A retrospective cohort study of 12899 women who underwent a GCT (24-28 weeks). Women with a low-GCT result (<10th percentile (70mg/dL) were compared to women with normal-GCT result (70-140mg/dL). ROC analysis was used to determine the optimal lower GCT threshold for the prediction of growth restriction. Results: Women in the low GCT had significant lower rates of cesarean delivery (18.7% versus 22.5%), shoulder dystocia (0.0% versus 0.3%), mean birthweight (3096±576 versus 3163±545) and birthweight percentile (49.1±27.0 versus 53.1±26.7) and significant higher rates of birthweight <2500g (11.3% versus 8.5%), below the 10th percentile (8.3% versus 6.5%) and 3rd percentile (2.3% versus 1.4%). Low GCT was independently associated with an increased risk for birthweight <2500g (OR=1.6, 1.2-2.0), birthweight <10th percentile (OR=1.3, 1.1-1.6), birthweight <3rd percentile (OR=1.7, 1.2-2.5) and neonatal hypoglycemia (OR=1.4, 1.02-2.0). The optimal GCT threshold for the prediction of birthweight <10th percentile was 88.5mg/dL (sensitivity 48.5%, specificity 58.1%). Conclusion: Low-GCT result is independently associated with low birthweight and can be used in combination with additional factors for the prediction of fetal growth restriction.