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Original Investigation
March 26, 2019

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

Author Affiliations
  • 1Division of Pediatrics, Department of Clinical Science, Intervention, and Technology, Karolinska Institutet, Stockholm, Sweden
  • 2Department of Neonatal Medicine, Karolinska University Hospital, Stockholm, Sweden
  • 3Swedish Neonatal Quality Register, Umeå University Hospital, Umeå, Sweden
  • 4Departments of Clinical and Experimental Medicine and Pediatrics, Linköping University, Linköping, Sweden
  • 5Departments of Clinical Sciences and Pediatrics, Lund University and Skåne University Hospital, Lund, Sweden
  • 6Departments of Clinical Sciences and Pediatrics, Umeå University, Umeå Sweden
  • 7Department of Women’s and Children’s Health, Uppsala University, Uppsala, Sweden
  • 8Department of Pediatrics, Ryhov County Hospital, Jönköping County Council, Jonkoping, Sweden
  • 9Centre for Reproductive Epidemiology, Lund University, Lund, Sweden
  • 10Departments of Clinical Sciences and Obstetrics and Gynecology, Lund University, Skåne University Hospital, Lund, Sweden
  • 11Division of Clinical Epidemiology, Department of Medicine, Karolinska Institutet, Stockholm, Sweden
  • 12Division of Obstetrics and Gynecology, Department of Women’s and Children’s Health, Karolinska Institutet, Stockholm, Sweden
  • 13Department of Pediatrics, Institute for Clinical Sciences, Queen Silvia Children’s Hospital, Sahlgrenska Academy, Göteborg University, Göteborg, Sweden
  • 14Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, Stockholm, Sweden
  • 15Sachs’ Children and Youth Hospital, Department of Neonatal Medicine, Södersjukhuset, Stockholm, Sweden
JAMA. 2019;321(12):1188-1199. doi:10.1001/jama.2019.2021
Key Points

Question  Has survival after extremely preterm birth changed in Sweden from 2004-2007 to 2014-2016?

Findings  In this comparison of 2 birth cohorts in Sweden that included 2205 births at 22-26 weeks’ gestational age, 1-year survival among those born alive in 2004-2007 was 70% compared with 77% for those born alive in 2014-2016 and the difference was statistically significant.

Meaning  In Sweden, 1-year survival after extremely preterm birth improved between 2004-2007 and 2014-2016.

Abstract

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.

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