Trends in Postmenstrual Age at Discharge and Predictive Factors Among a Contemporary Cohort of Infants Born Preterm

To evaluate contemporary trends in postmenstrual age (PMA) at discharge among infants born at 23-33 completed weeks' gestation and to examine which factors predict discharge PMA by birth gestational age (GA).

This retrospective, observational cohort study used Epic Systems Cosmos data. Infants born from January 1, 2017 to December 31, 2023, at 23 + 0 to 33 + 6 weeks' gestation, who were not transferred and survived to discharge were included. We examined discharge PMA annually stratified by birth GA categories (23-24, 25-26, 27-28, 29-30, and 31-33 weeks) and assessed trends using linear mixed models. Random forest models examined factors predicting discharge PMA.

Median discharge PMA increased over the study period by 3.4 days (95% CI: 3.1-3.8). Trends varied by GA, with the highest increase of 6.4 days (95% CI: 2.1-10.8) for infants born at 23-24 weeks and the lowest 2.3 days (95% CI: 1.8-2.6) for infants born at 31-33 weeks. Among all infants, the 3 most important factors predicting discharge PMA were: GA, bronchopulmonary dysplasia (BPD) diagnosis, and mechanical ventilation. When examining factors by GA category, the 3 most important factors for infants born at 23-24 weeks were: BPD diagnosis, birth hospital unit, and ventilation; for infants born at 31-33 weeks, they were ventilation, caffeine administration, and BPD diagnosis. Unit was also predictive of discharge PMA in all GA categories.

Median discharge PMA increased among all infants born preterm. Although indicators of illness were expected predictors of discharge PMA, the importance of unit on discharge PMA within GA strata suggests that practice variation plays a significant role in discharge timing.