Selection Bias and Outcomes for Preterm Neonates

Abstract

BACKGROUND: Reported survival and neurodevelopmental outcomes at 23 weeks’ gestation are based on the infants admitted to NICUs. In this study, we aim to describe the association between clinical characteristics and admission to NICU at 23, 24 and 25 weeks’ gestation. METHODS: Cohort data from 2 national databases enabled comparison of the clinical characteristics all Australian births and all NICU admissions during 2010–2013 at 23, 24, and 25 weeks’ gestation. RESULTS: NICU admission occurred in 15% of all births at 23 weeks, in comparison with 49% at 24 weeks and 64% at 25 weeks. At 23 weeks, live-born infants were less likely to be admitted to NICU with birth weight <500 g compared with >500 g (13% vs 43%, P < .0001), and boys were admitted less compared with girls (33% vs 43%, P < .018). In contrast, birth weight (including birth weight <500 g) and sex had little or no impact on NICU admission at 24 and 25 weeks. Only 8% of live births were born by caesarean delivery at 23 weeks compared with 33% at 24 weeks and 48% at 25 weeks’ gestation. CONCLUSIONS: In the Australian population, admission to the NICU is more likely to be influenced by birth weight and sex at 23 weeks’ gestation when compared with 24 and 25 weeks’ gestation. Survival outcomes at 23 weeks may be affected by less active perinatal care. Uncertainty exists regarding the generalizability of current data regarding survival and developmental potential of live-born 23-week infants.