Assessing the potential impact of extending antenatal steroids to the late preterm period

In 2016, guidance statements were issued by the Society for Maternal-Fetal Medicine and the American Congress of Obstetricians and Gynecologists about extending antenatal steroid use to selected late preterm singleton pregnancies.

We sought to review antenatal steroid use prior to the 2016 guidance statements and assess the potential impact of these.

This cohort study used chart-abstracted data from singleton deliveries from Jan. 1, 2012, through March 31, 2016, at 12 centers participating in the Obstetrics Clinical Outcomes Assessment Program, a quality initiative in Washington State. Pregnancies with missing gestation at delivery, fetal anomalies, or antepartum demise were excluded. Antenatal steroid use prior to the 2016 guidance was evaluated based on the percentage of early preterm deliveries (23⁺⁰-33⁺⁶ weeks) and the percentage of all pregnancies that received antenatal steroids. Newborn complication rates were calculated for late preterm deliveries (34+0⁺⁰-36⁺⁶ weeks), grouped by whether they would be potentially eligible or ineligible for antenatal steroids based on the 2016 guidance statements.

The opportunity for antenatal steroids was missed in 21.8% (226/1034) of early preterm deliveries and of all those who received antenatal steroids, 32.2% (614/1908) delivered at term. Of preterm deliveries, 74% (n = 2942) were in the late preterm period. In all, 80% (n = 2363) of late preterm deliveries were potentially eligible for antenatal steroids and 60% of these (n = 1411) delivered at 36 weeks. The rate of respiratory complications in newborns delivering at 34 and 35 weeks was higher in the group potentially eligible for late preterm antenatal steroids compared to those in the ineligible group. Of those delivering at 36 weeks, no differences were detected in prevalence of respiratory complications by potential eligibility for antenatal steroids; however, compared with the ineligible group, those potentially eligible had a lower risk of neonatal intensive care unit admission (P < .001). More than two thirds (69%; 171/248) of newborn respiratory complications among late preterm deliveries potentially eligible for antenatal steroids occurred in those delivering at 34-35 weeks. The highest rate of respiratory complications was in those ineligible for antenatal steroids due to prepregnancy diabetes or chorioamnionitis, regardless of gestational age at delivery.

Careful consideration of which pregnancies should receive late preterm antenatal steroids and how to identify these pregnancies is important to optimize benefits and mitigate potential risks of this intervention.