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OBJECTIVE To assess the effect of tight compared with liberalized intrapartum maternal glucose management on neonatal hypoglycemia risk in pregnancies complicated by gestational diabetes mellitus (GDM). METHODS This was a randomized controlled trial of women with singleton gestations and GDM attempting vaginal delivery. After written informed consent, women were randomly allocated to one of two intrapartum maternal glucose management protocols: tight control (glucose measurements hourly and treatment for maternal glucose levels lower than 60 mg/dL or greater than 100 mg/dL) or liberalized control (glucose measurements every 4 hours and treatment for maternal glucose levels lower than 60 mg/dL or greater than 120 mg/dL). The primary outcome was the first neonatal blood glucose level; a total sample size of 74 was necessary to have 80% power to detect a mean difference of 10 mg/dL between groups. Secondary outcomes included neonatal blood glucose concentrations within the first 24 hours of life, number of glucose treatments (intravenous or oral) received to treat neonatal hypoglycemia, neonatal intensive care unit admission, and neonatal hyperbilirubinemia. RESULTS From February 2016 to April 2018, 76 women were randomized (38 in each group), and all were included in the analysis. Baseline characteristics of the two groups were comparable for all relevant obstetric variables; mean gestational age was 39 weeks in both groups. Antepartum, two thirds of women in each group were treated medically (almost exclusively with insulin). The primary outcome was similar between the tight and liberalized control groups: 53 mg/dL vs 58 mg/dL, mean difference -4.18, 95% CI -12.66 to 4.29. However, mean neonatal glucose level within the first 24 hours of life was lower in the tight control group: 54 mg/dL vs 58 mg/dL, mean difference -3.39, 95% CI -7.07 to 0.29. Other secondary outcomes were similar between groups. CONCLUSION A protocol aimed at tight maternal glucose management in labor compared with liberalized management for women with GDM did not result in better initial neonatal glucose concentrations and was associated with lower mean neonatal blood glucose levels in the first 24 hours of life. This study supports raising the upper threshold for intrapartum maternal glucose and decreasing the frequency of intrapartum glucose assessment for women with GDM. CLINICAL TRIAL REGISTRATION ClinicalTrials.gov, NCT02596932.