Neonatal Morbidity and 1-Year Survival of Extremely Preterm Infants.

Objective: To determine 1-year survival and major neonatal morbidities (intracranial hemorrhage grade >2, cystic periventricular leukomalacia, retinopathy of prematurity grade >2, necrotizing enterocolitis, severe bronchopulmonary dysplasia) among extremely preterm infants in Norway in 2013-2014, and to compare the results to the first Norwegian Extreme Prematurity Study 1999-2000 and similar contemporary European population-based studies.

Methods: Population-based study of all infants born at 22 through 26 weeks' gestation in Norway in 2013-2014. Prospectively collected data were obtained by linking data in the Norwegian Neonatal Network to the Medical Birth Registry of Norway.

Results: Of 420 infants (incidence 3.5 per 1000 births), 145 were stillborn (34.5%), 275 were live-born (82.3% of the 334 fetuses alive at admission for obstetrical care), and 251 (91.3% of live-born infants) were admitted to a neonatal unit. The survival among live-born infants was 18% at 22 weeks, 29% at 23 weeks, 56% at 24 weeks, 84% at 25 weeks and 90% at 26 weeks (for each week increment in gestational age: odds ratio 3.3; 95% confidence interval, 2.4-4.4). Among infants surviving to 1 year of age, major neonatal morbidity was diagnosed in 55%. Decreasing gestational age was moderately associated with rates of major morbidity (odds ratio 1.6; 95% confidence interval, 1.2-2.2).

Conclusions: Compared to the previous 1999-2000 cohort, the rate of stillbirth before admission to an obstetrical unit increased, whereas the survival rate among live born infants was similar in our 2013-2014 cohort. Neonatal morbidity rates remain high among extremely preterm infants.