136 - Histologic chorioamnionitis in the setting of antenatal steroids is associated with decreased incidence of severe respiratory distress syndrome in preterm infants

Chorioamnionitis is a common cause of preterm birth. Currently, antenatal steroids (ANS) are administered to 76-85% of mothers with threatened preterm birth. In large animal models of prematurity, combined exposure to chorioamnionitis and ANS enhances lung maturation compared to either exposure alone. However, the effect of chorioamnionitis in the setting of ANS on the initial respiratory failure after preterm birth have not been well examined. 

Objective: To evaluate the association between histologic chorioamnionitis (HCA) and severe RDS (sRDS) in the setting of ANS in preterm infants.

Design/Methods:

Data from infants of 23-30 w gestational age (GA) admitted to the Holtz Children’s Hospital NICU at University of Miami/Jackson Memorial Medical Center from Jan 2012 to Dec 2021 were analyzed. ANS was classified into two groups: No ANS or ANS given >7 days before birth (ANS-) and ANS given within 7 days before birth (ANS+). HCA+ was determined by placental pathology. sRDS was defined as respiratory support with FiO2 ≥.30 on postnatal day 1. Pearson’s Chi-square test was used for univariate analysis of categorical variables and Mantel Haenszel test to analyze across strata. Multivariate logistic regression was used to model the association between HCA and ANS with sRDS.

Results: The cohort included 1218 infants of whom 441 (36%) were born to mothers with HCA and 1136 (93%) received ANS. 216 infants (18%) had sRDS. The incidence of sRDS was lower in the HCA+ than in the HCA- group and this was more pronounced within the ANS- subgroup (Figure 1). Multivariate analysis showed HCA+, ANS+ and the combination of both were independently associated with decreased risk of sRDS (Figure 2). Higher GA was also associated with decreased risk for sRDS whereas small for gestational age (SGA, BW < 10th percentile) was associated with increased risk. Race, gender, Hispanic ethnicity and pre-eclampsia were not associated with sRDS risk.

Conclusion(s): In this cohort of preterm infants, HCA was associated with a decreased incidence of sRDS of magnitude similar to ANS treatment. HCA and ANS given within 7 days of preterm birth were associated with a decreased risk of sRDS. The reduction in risk was more striking in the HCA and ANS were combined. These findings are consistent with experimental observations of improved lung maturation with combined exposure to HCA and ANS. The additive effect of these exposures suggests independent and complementary molecular mechanisms of action. More studies are needed to better understand the mechanisms by which HCA and ANS interact, leading to enhanced maturation of the preterm lung.