178: The effect of antenatal corticosteroid administration on neonatal biometrics administered after 34 weeks gestation


      Whereas evidence suggests that the administration of repetitive doses of antenatal corticosteroids to mothers at risk for preterm birth reduces newborn cephalic biometric measures, a single course followed by a rescue regimen before 34 0/7 weeks gestation has not demonstrated this effect and has proven to be beneficial for the fetus at risk for preterm birth. Currently, there are no studies that have evaluated the effects of antenatal corticosteroid on newborn biometric measurements given after 34 0/7 weeks gestation for women at risk for late-preterm birth.

      Study Design

      A retrospective chart review of all newborns born at Ben Taub and Baylor Texas Children’s Pavillion for Women, Houston, TX between January 2011 and June 2017 was performed. Newborns were stratified according to the administration of a course of maternal antenatal corticosteroids after 34 0/7 weeks gestation or not at all and matched for gestational age at birth. Women with any significant medical history, antenatal complications or multiple gestation were excluded from analysis, as were newborns with anomalies or genetic syndromes. Available data for all of women’s pregnancies were included. Groups of interest were compared by linear mixed models. All confounders were controlled for and included in the regression model.


      During the time period, 670 women and newborn pairs were identified. The mean gestational age at delivery for women who received betamethasone was not significantly different compared to those who did not (36.1 vs. 36.3 weeks, p<.109). Of these pairs, 367 women did not receive betamethasone and 303 received only a single course. Within that subcohort, 243 received their course prior to 34 weeks and 60 after. There was no significant difference between birthweight, length or head circumference between newborns born to women who received a course of antenatal corticosteroids ≥ 34 weeks gestation versus those who did not and delivered at the same gestational age.


      This data provides reassuring data concerning the effects of late preterm antenatal corticosteroid administration on neonatal biometric measurements.
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