Are Newborn Outcomes Different for Term Babies Who Were Exposed to Antenatal Corticosteroids?

The administration of antenatal corticosteroids can improve newborn lung function following antenatal treatment of pregnant women who are between 24 and 36 + 6/7 weeks' gestation and at risk of preterm delivery within 7 days. Antenatal corticosteroids, such as betamethasone (BMZ), reduce the risks of respiratory distress syndrome, the need for respiratory support, and admission to the neonatal intensive care unit (NICU). They also lower the risk of other complications related to preterm delivery such as intraventricular hemorrhage, necrotizing enterocolitis, and neonatal death. However, the ability to predict which women are mostly likely to deliver prematurely and who will ultimately carry to term (>= 37 weeks) is imprecise, and the effect of BMZ on at-term infants is unclear. This study aimed to compare the outcomes of term infants exposed to BMZ in utero with those who were not exposed to BMZ in mothers diagnosed with threatened preterm delivery. This was a retrospective cohort study of infants born between 2012 and 2019 in 1 health system in Indianapolis, Ind. Included were infants who were born at term to mothers with threatened preterm labor. Comparisons were made between those infants with exposure to BMZ in utero and those without exposure. The primary outcomes were transient tachypnea of the newborn (TTN), admission to the NICU, and classification as small for gestational age (SGA). Of the 5330 women included in the cohort, 1459 (27.4%) were administered antenatal BMZ. In the unadjusted analysis, more infants exposed to BMZ in utero had a TTN diagnosis (5.1% vs 3.6%, respectively; P = 0.018) or were classified as SGA (19.6% vs 12.2%, respectively; P < 0.001) than those without exposure. They were also more likely to be admitted to the NICU (12.3% vs 6.4%, respectively; P < 0.001). After adjusting for covariates including maternal age, race, insurance, maternal conditions, and estimated gestational age at delivery, no significant difference was observed in TTN diagnosis between the groups (adjusted odds ratio [aOR], 1.10; 95% confidence interval [CI], 0.80-1.51). Infants exposed to BMZ were, however, more likely to be admitted to the NICU (aOR, 1.49; 95% CI, 1.19-1.86) and to be classified as SGA (aOR, 1.78; 95% CI, 1.48-2.14) than those with no exposure. In conclusion, infants born to mothers who received BMZ for threatened preterm delivery were at higher risk of NICU admission and being classified as SGA in both unadjusted and adjusted analyses. Betamethasone exposure was not associated with increased TTN diagnosis after adjusting for covariates. These results suggest that caution should be used in administering BMZ in women threatened with preterm delivery, given the risks to infants who are eventually born at term. Research should also focus on developing robust tools to determine which women with threatened preterm delivery will actually deliver within 7 days.

Automated summary

Administration of antenatal corticosteroids can improve lung function in infants at risk of preterm delivery. However, there are risks associated with their use, including increased likelihood of NICU admission and being classified as small for gestational age. Caution should be used in administering these drugs, and further research is needed to accurately predict the timing of preterm delivery in high-risk women.