Euglycemia after antenatal late preterm steroids: a multicenter, randomized controlled trial

BACKGROUND: Late preterm steroid administration can induce transient maternal and thus fetal hyperglycemia, which can increase production of fetal insulin and C-peptide. Infants delivered in this setting are subsequently at increased risk for hypoglycemia. Although maternal glycemic control before delivery is a key component of care for parturients with diabetes, this intervention has not been studied in the setting of late preterm steroid administration. OBJECTIVE: This study aimed to determine the effect of maternal screening for and treatment of hyperglycemia after late preterm steroid administration on fetal C-peptide levels and other metabolic markers. STUDY DESIGN: This was a multicenter, randomized trial (NCT03076775) of nondiabetic parturients with a singleton gestation receiving betamethasone at 34 0/7 weeks to 36 5/7 weeks for anticipated preterm birth. Participants randomized to maternal glycemic control received fasting and 1-hour postprandial or serial intrapartum capillary blood glucose screening with insulin treatment as indicated. Those randomized to expectant management did not receive any glucose screening or treatment. The primary outcome was fetal C-peptide level measured from umbilical cord blood at delivery. Secondary outcomes included other fetal metabolic markers and neonatal hypoglycemia (glucose level <40 mg/dL). Baseline characteristics and outcomes were compared between the groups. We estimated that we would need a sample size of 144 to provide >90% power to show a 1 ng/mL decrease in C-peptide concentration (+/- 1.5 ng/mL) at alpha=0.05 using a 2-sample t test and 1 interim analysis. After the interim analysis, the trial was stopped for futility. RESULTS: Of 491 screened parturients, 163 (33%) were deemed eligible and 86 (53%) were randomized to 1 of the treatment groups (June 2017 to February 2021). One person was lost to follow-up because of delivery at another hospital. Baseline characteristics were similar between groups. The median interval from betamethasone administration to delivery was 24 hours (interquartile range, 13-96 hours) and did not differ between groups (P=.82). Most (82%) randomized to maternal glycemic control had hyperglycemia: 80% had at least 1 fasting glucose level >95 mg/dL, 75% had at least one 1-hour postprandial glucose level >140 mg/dL, and 80% had at least 1 intrapartum glucose level >110 mg/dL. In addition, 15% had at least 1 glucose level >180 mg/dL. None had maternal hypoglycemia after insulin treatment. Compared with expectant management, maternal glycemic control did not affect the median fetal C-peptide level (1.02; interquartile range, 0.52-1.85 vs 1.09; interquartile range, 0.61-1.65; P=.97) or other metabolic markers. Maternal glycemic control also did not affect neonatal hypoglycemia (49% vs 51%; P=.83) or other secondary neonatal or maternal outcomes. There was no evidence of effect modification by gestational age or body mass index at randomization, indication for betamethasone, duration from betamethasone to delivery, maternal race or ethnicity, or neonatal sex. In addition, the results were unchanged in a sensitivity analysis using a per protocol approach. CONCLUSION: Maternal hyperglycemia was observed in most nondiabetic parturients after receiving late preterm betamethasone. However, there was no improvement in fetal metabolic status, neonatal hypoglycemia, or other neonatal or maternal outcomes with maternal glycemic control. Therefore, maternal glucose surveillance and treatment does not seem to be beneficial in nondiabetic parturients receiving late preterm steroids.