(909) Optimally timed antenatal corticosteroids over a 5-year period in a large US birth cohort

Objective: Antenatal corticosteroids (ACS) improve outcomes for preterm neonates and are most effective when administered within the 7 days preceding preterm birth. ACS also have an uncertain long term safety profile for babies born at term. Optimizing ACS is therefore important to maximize benefits and minimize potential harm. Our objective was to evaluate optimal ACS use in a contemporary US birth cohort over a 5-year period.

Study Design: This retrospective observational study included consecutive births (24⁺⁰-42⁺⁶ weeks’ gestation) at 12 hospitals in the Northwest US (Jan 2017-Dec 2021). Pregnancies missing data for ACS (n=153) were excluded. ACS exposure was based on >=1 dose of a first course of ACS. Clinical data were collected from medical records.  The outcomes evaluated were: optimally timed ACS in
early preterm births (ACS given within 7 days of live births < 34 weeks, expressed as a % of all live births < 34 weeks); % of

term births given ACS; and % of late preterm (34⁺⁰-36⁺⁶weeks) live births given ACS within 7 days.  Overall and annual rates of each outcome were calculated. Univariate estimates of Odds Ratios (OR) and 95% Confidence Intervals (95% CI) were calculated for change over time with 2017 as the reference year.

Results: Our study comprised 106,146 births: 10,112 preterm and 96,034 term births. In all, 54.8% of early preterm and 27.2% of late preterm births were given ACS within 7 days; 1.3% of term births also received ACS. Between 2017 and 2021, the annual rate of optimally timed ACS in early preterm births remained unchanged while ACS within 7 days of late preterm births increased (OR 1.38; 95% CI 1.17, 1.63) (Table 1). ACS exposure in term births also increased from 1.0% to 1.7% (OR 1.66; 95% CI 1.39, 1.98). Of 1250 term births with timing of ACS, 41.3% received ACS at 34⁺⁰-36⁺⁶ weeks and 3.7% at term.

Conclusion: Given the suboptimal timing of ACS in preterm births and increasing ACS exposure in term births, our study highlights a need for greater focus on optimal timing of ACS and on strategies to avoid unnecessary ACS in term births.