Association Between Year of Birth and 1-Year Survival Among Extremely Preterm Infants in Sweden During 2004-2007 and 2014-2016

Importance Since 2004-2007, national guidelines and recommendations have been developed for the management of extremely preterm births in Sweden. If and how more uniform management has affected infant survival is unknown. Objective To compare survival of extremely preterm infants born during 2004-2007 with survival of infants born during 2014-2016. Design, Setting and Participants All births at 22-26 weeks’ gestational age (n = 2205) between April 1, 2004, and March 31, 2007, and between January 1, 2014, and December 31, 2016, in Sweden were studied. Prospective data collection was used during 2004-2007. Data were obtained from the Swedish pregnancy, medical birth, and neonatal quality registries during 2014-2016. Exposures Delivery at 22-26 weeks’ gestational age. Main Outcomes and Measures The primary outcome was infant survival to the age of 1 year. The secondary outcome was 1-year survival among live-born infants who did not have any major neonatal morbidity (specifically, without intraventricular hemorrhage grade 3-4, cystic periventricular leukomalacia, necrotizing enterocolitis, retinopathy of prematurity stage 3-5, or severe bronchopulmonary dysplasia). Results During 2004-2007, 1009 births (3.3/1000 of all births) occurred at 22-26 weeks’ gestational age compared with 1196 births (3.4/1000 of all births) during 2014-2016 ( P = .61). One-year survival among live-born infants at 22-26 weeks’ gestational age was significantly lower during 2004-2007 (497 of 705 infants 70%) than during 2014-2016 (711 of 923 infants 77%) (difference, −7% 95% CI, −11% to −2.2%, P = .003). One-year survival among live-born infants at 22-26 weeks’ gestational age and without any major neonatal morbidity was significantly lower during 2004-2007 (226 of 705 infants 32%) than during 2014-2016 (355 of 923 infants 38%) (difference, −6% 95% CI, −11% to −1.7%, P = .008). Conclusions and Relevance Among live births at 22-26 weeks’ gestational age in Sweden, 1-year survival improved between 2004-2007 and 2014-2016.