Abstract Background Since 2016 in the United States, antenatal steroids (AS) have been recommended for women at risk for delivering late preterm infants (LPIs, born between 34 0/7 and 36 6/7 weeks gestational age) to reduce early neonatal respiratory morbidity. But concerns remain about the potential benefits weighed against the risks of use due to knowledge gaps about longer-term outcomes. For LPIs, there is lack of physiologic lung function data between birth to 6 years of age, a period of exponential lung growth. Objective We aimed to quantify the potential association of AS on lung function at 6 months of age by measuring forced expiratory flows (FEFs) and volumes. We also followed clinical respiratory outcomes for the first year of life. Design/Methods Singleton LPIs delivered between June 2023 to August 2024 in 2 centers were consented and prospectively followed (IRB#25482). At 6 months corrected age, forced expiratory flows FEFs) and volumes were measured using the raised volume rapid thoracoabdominal compression (RVRTC) technique. Monthly standardized respiratory questionnaires (RQs) were administered through 12 months. Comparisons of the RVRTC outcomes of the two groups were performed using analysis of covariance adjusting for body length at testing, sex, race, and gestational age at delivery. Results Forty-four infants consented into the study at birth (18 AS, 26 NoAS). Twenty-seven infants (12 AS, 15 NoAS) returned with successful RVRTC measurements at 6 months corrected age. There were no significant differences in infant characteristics and early clinical outcomes between the two groups prior to discharge (Table 1A), or among those who completed RVRTCs. We found a 12.7% significant difference in FVC between the two groups (AS = 303.1 + 59.0 vs No AS = 341.6 + 70.0 mL, Mean ±SD; p 0.05) and an 8.9% difference in FEV0.5 (AS = 232.0 ± 43.2 vs No AS = 252.6±35.5; p 0.05). There was no difference in other FEFs. (Table 1B). A median number of 12 RQs were completed in both groups (Table 1C). Conclusion In this prospective cohort, AS-exposed LPIs had a significantly lower FVC and FEV0.5 when compared to non-exposed infants. These findings from our pilot study suggest that AS may impair growth and development of the lung parenchyma. Study limitations include cohort loss and unavoidable non-randomized nature. Given continued concerns of the negative effect of AS on long-term growth, a larger study that measures physiologic outcomes in addition to clinical outcomes is needed. This abstract is funded by: Oregon Clinical and Translational Research Institute KL2TR002370
Go et al. (Fri,) studied this question.