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

Educational Objective
To understand the potential benefits of improving the clinical management of extremely preterm births.
1 Credit CME
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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Article Information

Corresponding Author: Mikael Norman, MD, PhD, Division of Pediatrics, CLINTEC, Novum, Blickagången 6A, Karolinska Institutet, SE 141 57 Stockholm, Sweden (mikael.norman@ki.se).

Accepted for Publication: February 19, 2019.

Author Contributions: Drs Källén (2004-2007 cohort) and Håkansson (2014-2016 cohort) had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Norman, Abrahamsson, Björklund, Domellöf, Farooqi, Hellström-Westas, Källén, Maršál, Normann, Stigson, Um-Bergström, Håkansson.

Acquisition, analysis, or interpretation of data: Norman, Hallberg, Abrahamsson, Björklund, Domellöf, Farooqi, Foyn Bruun, Gadsbøll, Hellström-Westas, Ingemansson, Källén, Ley, Maršál, Normann, Serenius, Stephansson, Håkansson.

Drafting of the manuscript: Norman, Domellöf, Hellström-Westas, Källén, Ley.

Critical revision of the manuscript for important intellectual content: Hallberg, Abrahamsson, Björklund, Domellöf, Farooqi, Foyn Bruun, Gadsbøll, Hellström-Westas, Ingemansson, Källén, Ley, Maršál, Normann, Serenius, Stephansson, Stigson, Um-Bergström, Håkansson.

Statistical analysis: Norman, Farooqi, Källén, Håkansson.

Obtained funding: Norman, Hallberg, Normann.

Administrative, technical, or material support: Norman, Hallberg, Abrahamsson, Farooqi, Foyn Bruun, Ley, Stephansson, Stigson, Um-Bergström, Håkansson.

Supervision: Norman, Hallberg, Abrahamsson, Ley, Maršál, Serenius, Um-Bergström, Håkansson.

Other: Serenius.

Conflict of Interest Disclosures: Dr Norman reported receiving grants from the Swedish Heart Lung Foundation and the H2020/European Union; and receiving personal fees from a Swedish medical journal, the Swedish patient insurance, Liber AB, Studentlitteratur AB, and AbbVie AB. No other disclosures were reported.

Funding/Support: Funding for this study was provided by the Swedish Order of Freemasons’ Foundation for Children’s Welfare. The Swedish pregnancy, medical birth, and neonatal quality registries are funded by the Swedish government (ministry of health and social affairs) and the body of regional health care providers (county councils).

Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Additional Contributions: We thank all obstetric, pediatric, and ophthalmology departments in Sweden for contributing and sharing data with the quality registries. We are grateful to Kerstin Andersson, RN (Karolinska Institutet), and Fanny Söderström, MD (Uppsala University), for taking a large part in validating the Swedish neonatal quality registry data against medical records. Both received compensation for their role in the study.

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