Do maternal demographics and prenatal history impact the efficacy of betamethasone therapy for threatened preterm labor?

Background Betamethasone (BMZ) is used to accelerate fetal lung maturation in women with threatened preterm birth, but its efficacy is variable and limited by the lack of patient individualization in its dosing and administration. To determine sources of variability and potential opportunities for individualization of therapy, the objective of this study was to evaluate maternal factors associated with development of neonatal respiratory distress syndrome (RDS) in a cohort of women who received betamethasone. Methods This study prospectively enrolled women, gestational ages 23–34 weeks, who received betamethasone for threatened preterm birth. Maternal demographics, prenatal history, and neonatal outcomes were abstracted from hospital records. RDS was the primary outcome. Associations between RDS diagnosis and maternal demographics, prenatal history, and betamethasone dosing were evaluated in a case-control analysis and multivariable regression adjusted for gestational age at delivery. Secondary analyses limited the cohort to women who delivered within 1 or 2 weeks of betamethasone dosing. Results Of 209 deliveries, 90 (43 %) resulted in neonatal RDS. Within the overall cohort and controlling for gestational age at birth, RDS was only associated with cesarean births compared to vaginal births (adjusted OR 1.17 [1.06–1.29]). Route of delivery was also the only significant factor related to RDS in the 83 neonates delivered within 7 days of BMZ dosing. However, among 101 deliveries within 14 days of betamethasone dosing and controlling for gestational age at birth, women who experienced preterm premature rupture of membranes (PPROM) had lower RDS rates than those without PPROM (57.9 % vs. 80.2 %, adjusted OR 0.81 [0.67–0.99]). Maternal age, BMI, race, and ethnicity were not associated with RDS in the regression models. Conclusions Of maternal characteristics analyzed, only delivery by cesarean was associated with neonatal RDS after antenatal betamethasone use.