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Original research
Outcomes to 5 years of outborn versus inborn infants <32 weeks in Western Australia: a cohort study of infants born between 2005 and 2018
  1. Jonathan W Davis1,2,3,
  2. C E Seeber3,
  3. Elizabeth A Nathan4,
  4. Tobias Strunk3,5,
  5. Andy Gill2,3,
  6. Mary Sharp2,3
  1. 1 Newborn Emergency Transport Service of Western Australia, Perth Children's Hospital, Nedlands, Western Australia, Australia
  2. 2 School of Medicine, The University of Western Australia, Perth, Western Australia, Australia
  3. 3 Neonatal Directorate, Child and Adolescent Health Service, King Edward Memorial Hospital, Perth, Western Australia, Australia
  4. 4 Division of Obstetrics and Gynaecology, The University of Western Australia, Perth, Western Australia, Australia
  5. 5 Wesfarmers Centre for Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Western Australia, Australia
  1. Correspondence to Dr Jonathan W Davis, Newborn Emergency Transport Service of Western Australia, Perth Children's Hospital, Nedlands, WA 6009, Australia; jonathan.davis{at}uwa.edu.au

Abstract

Objective We compared mortality and morbidity of inborn versus outborn very preterm infants <32 weeks’ gestation in Western Australia (WA) between 2005 and 2018.

Design Retrospective cohort study.

Patients Infants <32 weeks’ gestation who were born in WA.

Main outcome measures Mortality was assessed as death before discharge home from the tertiary neonatal intensive care unit. Short-term morbidities included combined brain injury (intracranial haemorrhage grade ≥3 and cystic periventricular leukomalacia) and other major neonatal outcomes. Developmental assessments at age 2, 3 and 5 years were evaluated. We performed multivariable logistic regression analysis of outborn status on outcomes, controlling for gestational age, birth weight z-score, sex and multiple birth.

Results A total of 4974 infants were born in WA between 22 and 32 weeks’ gestation between 2005 and 2018 of which 4237 (89.6%) were inborn and 443 (10.4%) were outborn. Overall mortality to discharge was higher in outborn infants (20.5% (91/443) vs 7.4% (314/4237); adjusted OR (aOR) 2.44, 95% CI 1.60 to 3.70, p<0.001). Outborn infants had higher rates of combined brain injury than those inborn (10.7% (41/384) vs 6.0% (246/4115); aOR 1.98, 95% CI 1.37 to 2.86), p<0.001). No difference in up to 5-year developmental measures was detected. Follow-up data were available for 65% of outborn and 79% of inborn infants.

Conclusions Outborn preterm infants <32 weeks in WA had increased odds of mortality and combined brain injury than those inborn. Developmental outcomes up to 5 years were similar between groups. Loss to follow-up may have impacted the long-term comparison.

  • intensive care units, neonatal
  • neonatology
  • child development
  • mortality
  • infant development

Data availability statement

Data are available on reasonable request.

https://doi.org/10.1136/archdischild-2022-324749

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    Data availability statement

    Data are available on reasonable request.

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    Footnotes

    • Twitter @jonathan_davis3

    • Contributors JWD designed the original concept, interpreted results, drafted and revised the manuscript and approved for final submission. JWD acts as guarantor for this work. CES designed the original concept, the acquisition of data, interpreted results, revised the manuscript and approved for final submission. EAN assisted in the design of the original concept, acquisition and analysis of the data, revision of the manuscript and approval of final submission. TS assisted in designing the original concept, interpreting the result, revising the manuscript and approval for final submission. AG assisted in designing the original concept, interpreting the result, revising the manuscript and approval for final submission. MS designed the original concept, interpreted results, drafted and revised the manuscript and approved for final submission.

    • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

    • Competing interests None declared.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.