National Trends in Survival and Short-term Outcomes of Periviable Births ≤24 Weeks Gestation in the United States, 2009-2018

Background: Few studies from some academic centers in the United States (US) have demonstrated increased survival of periviable preterm infants during the recent decade. However, this cannot be extrapolated to the national level due to variations in institutional policies and practices related to perinatal care and initiation and withdrawal of care. The objective was to examine the short-term outcomes and national trends in survival to discharge of extremely preterm infants born at ≤24 weeks gestation in the US from 2009 – 2018. Such population-based outcomes can aid in prognostication and counseling families with periviable infants.

Methods: This was a retrospective, repeated cross-sectional analysis of hospital discharges within the Healthcare Cost and Utilization Project’s National Inpatient Sample for preterm infants ≤24 weeks gestational age (GA) from 2009 – 2018. Infants with survival <24 hours or implausible birthweights were excluded. The primary outcome was the trend in survival to discharge. The secondary outcome was the composite of death prior to discharge or major morbidity defined by ≥1 of the following: bronchopulmonary dysplasia, necrotizing enterocolitis stage ≥2, periventricular leukomalacia, severe intraventricular hemorrhage, severe retinopathy of prematurity, tracheostomy, ventriculoperitoneal shunt, and gastrostomy tube placement. Bivariate analysis was used to compare these outcomes between those born at ≤23 weeks and those born at 24 weeks GA. Cochran-Armitage trend test was used for trend analysis and p-value <0.05 was considered significant for all analyses.

Results: Among a total of 71,854 preterm infants ≤24 weeks GA, 34,117 (47.5%) died within 24hrs and were excluded from the study. Almost 93% of those who died within 24 hours were ≤23 weeks GA. Among the 37,031 included in the study cohort, 48.1% were of 24 weeks GA and they were more likely to have cesarean delivery (53.4% vs 28.0% for ≤23 weeks GA). Survival to discharge among those GA ≤ 23 weeks increased from 29.6% in 2009 to 41.7% in 2018 (P <0.001). Similarly, survival to discharge for GA 24 weeks increased from 58.3% in 2009 to 65.9% in 2018 (P <0.001). As shown in Table 1, all the composite outcomes (death or major morbidity) were significantly higher in the infants born at <23 weeks GA as compared to 24 weeks GA (P <0.001).

Conclusion: Survival to discharge among preterm infants who survived the first 24 hours of life significantly increased from 2009-2018. The composite outcome of mortality prior to discharge or severe morbidity remains higher especially in those born at ≤23 weeks GA. Further studies are needed to examine the post-discharge survival, healthcare resource use, and long neurodevelopmental outcomes of these periviable infants.