Mortality and serious morbidity rates for outborn compared with inborn 23-27 week infants

Background: Our aim was to report livebirths, NICU admissions, infant mortality and serious morbidity rates for outborn compared with inborn 23–27 week gestation infants in Victoria.
Method: A population-based cohort study of 23–27 week livebirths, free of lethal anomalies in 2010–2011 was conducted prospectively in all tertiary NICUs. The Consultative Council on Obstetric and Paediatric Mortality and Morbidity provided the denominators for all livebirths and deaths. Mortality and morbidity data for outborn compared with inborn infants admitted to NICU were analysed by logistic regression, adjusted for gestational age, birthweight and sex.
Results: 497 livebirths were recorded: 68 (13.7%) were outborn. Overall, 48.5% of outborns and 26% of inborns died (OR 2.63, 95% CI 1.56, 4.44, p < 0.001). 73% of outborns versus 93% of inborns were admitted to NICU. Mortality rates were lower for infants admitted to NICU: 24% of outborns and 19% of inborns (aOR 1.65, 95% CI 0.78, 3.51, p = 0.190). There were no significant differences in the risk of necrotising enterocolitis (aOR 0.94, 95% CI 0.35, 2.53, p = 0.902), intraventricular haemorrhage (aOR 1.88, 95% CI 0.98, 3.58, p = 0.056), the combined outcome of death or bronchopulmonary dysplasia (aOR 0.94, 95% CI 0.58, 1.53, p = 0.813) or death or retinopathy of prematurity (aOR 0.97, 95% CI 0.50, 1.85, p = 0.917). Outborn infants had an increased risk of periventricular leukomalacia compared with inborns (aOR 5.51, 95% CI 1.89, 16.01, p < 0.001).
Conclusions: Outborn infants admitted to NICU did not have significantly different rates of mortality or serious morbidity compared with inborns, with the exception of periventricular leukomalacia.