Antenatal dexamethasone versus betamethasone on glycemic control in mild gestational diabetes: A randomized clinical trial.

Background: Preterm births and gestational diabetes are common complications in pregnancy. A widely known side effect of antenatal corticosteroids (ACS) for fetal maturity in preterm births is maternal hyperglycemia. The choice of ACS regimens between dexamethasone and betamethasone highly depends on local availability and cost as current but inconclusive evidence show similar neonatal outcomes for both regimes.

Objective: To compare four 6-mg doses 12 hours apart antenatal dexamethasone versus two 11.4-mg doses 24 hours apart antenatal betamethasone regimens in medical nutrition therapy controlled gestational diabetes mellitus (GDM) cases on maternal glycemic response for up to three consecutive days after administration.

Methods: This is a randomized controlled clinical trial conducted between February 2021-August 2023 in a tertiary university hospital in Malaysia. Pregnant participants with diet-controlled GDM and prescribed ACS were randomized to either four 6-mg doses 12 hours apart dexamethasone or two 11.4-mg doses 24 hours apart betamethasone regimens. Self-monitoring of capillary blood glucose monitoring (6-points per 24 hours: pre- and 2 hours post-meal for the three main meals) was started after the first dose of allocated ACS. Hyperglycemia was defined as fasting or pre-meal glucose ≥5.3mmol/L (≤95mg/dL) or 2-hour post-meal glucose ≥6.7mmol/L (120 mg/dL). The primary outcomes were the number hyperglycemic episodes in the first and second 24 hours following ACS. Analyses were performed using t-test, Mann-Whitney-U test, and Chi-square test as appropriate.

Results: Median [interquartile range (IQR)] hyperglycemic episodes were similar 4 [2.3-5.0] vs. 4 [3.5-5.0], p=0.168 on Day-1, significantly lower on Day-2 (4 [3.0-5.0] vs. 5 [4.0-5.0], p=0.002) and Day-3 (1 [0.0-2.0] vs. 2.0 [1.0-3.0], p<0.001) in dexamethasone arm compared to betamethasone arm respectively. Median blood glucose levels were also significantly lower in dexamethasone group on Day-1 (Median [IQR] 6.3 [5.8-7.0] vs. 6.7 [6.3-7.0], p=0.016), Day-2 (6.4 [6.0-6.9] vs. 6.7 [6.3-7.2], p=0.001), and Day-3 (5.2 [4.8-5.5] vs. 5.7 [5.4-6.0], p<0.001) compared to betamethasone group. Mean blood glucose levels were higher throughout the 3-day study period in the betamethasone arm (6.2 mmol/L 97.5% CI 6.0-6.4 vs. 6.6 mmol/L 97.5% CI 6.4-6.7, mean difference -0.374 97.5% CI -0.521 to -0.226), p<0.001). Other maternal and neonatal outcomes were not significantly different across groups.

Conclusions: In GDM on medical nutrition therapy, dexamethasone ACS therapy could be preferred over betamethasone as hyperglycemic episodes on Day 2 and 3 post-treatments were fewer and median blood glucose levels were lower through to Day 3.