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Association between Apgar scores of 7 to 9 and neonatal mortality and morbidity: population based cohort study of term infants in Sweden

BMJ 2019; 365 doi: https://doi.org/10.1136/bmj.l1656 (Published 07 May 2019) Cite this as: BMJ 2019;365:l1656

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The Apgar score and association with neonatal mortality and morbidity

  1. Neda Razaz, postdoctoral fellow1,
  2. Sven Cnattingius, professor1,
  3. KS Joseph, professor2
  1. 1Division of Clinical Epidemiology, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
  2. 2Department of Obstetrics & Gynaecology, School of Population and Public Health, University of British Columbia and the Children’s and Women’s Hospital of British Columbia, Vancouver, BC, Canada
  1. Correspondence to: N Razaz neda.razaz{at}gmail.com
  • Accepted 20 March 2019

Abstract

Objective To investigate associations between Apgar scores of 7, 8, and 9 (versus 10) at 1, 5, and 10 minutes, and neonatal mortality and morbidity.

Design Population based cohort study.

Setting Sweden.

Participants 1 551 436 non-malformed live singleton infants, born at term (≥37 weeks’ gestation) between 1999 and 2016, with Apgar scores of ≥7 at 1, 5, and 10 minutes.

Exposures Infants with Apgar scores of 7, 8, and 9 at 1, 5, and 10 minutes were compared with those with an Apgar score of 10 at 1, 5, and 10 minutes, respectively.

Main outcome measures Neonatal mortality and morbidity, including neonatal infections, asphyxia related complications, respiratory distress, and neonatal hypoglycaemia. Adjusted odds ratios (aOR), adjusted rate differences (aRD), and 95% confidence intervals were estimated.

Results Compared with infants with an Apgar score of 10, aORs for neonatal mortality, neonatal infections, asphyxia related complications, respiratory distress, and neonatal hypoglycaemia were higher among infants with lower Apgar scores, especially at 5 and 10 minutes. For example, the aORs for respiratory distress for an Apgar score of 9 versus 10 were 2.0 (95% confidence interval 1.9 to 2.1) at 1 minute, 5.2 (5.1 to 5.4) at 5 minutes, and 12.4 (12.0 to 12.9) at 10 minutes. Compared with an Apgar score of 10 at 10 minutes, the aRD for respiratory distress was 9.5% (95% confidence interval 9.2% to 9.9%) for an Apgar score of 9 at 10 minutes, and 41.9% (37.7% to 46.4%) for an Apgar score of 7 at 10 minutes. A reduction in Apgar score from 10 at 5 minutes to 9 at 10 minutes was also associated with higher odds of neonatal morbidity, compared with a stable Apgar score of 10 at 5 and 10 minutes.

Conclusions In term non-malformed infants with Apgar scores within the normal range (7 to 10), risks of neonatal mortality and morbidity are higher among infants with lower Apgar score values, and also among those experiencing a reduction in score from 5 minutes to 10 minutes (compared with infants with stable Apgar scores of 10).

Footnotes

  • Contributors: NR and SC had full access to all the data in the study and take full responsibility for the integrity of the data and the accuracy of the data analysis. They are the guarantors. NR, SC, and KSJ conceived and designed the study. All authors interpreted the data and critically revised the manuscript for important intellectual content. NR drafted the manuscript and carried out the statistical analysis. SC obtained funding and provided administrative, technical, or material support.

  • Funding: This study was funded by the Swedish Research Council for Health, Working Life and Welfare (grant No 2017-00134), and by an unrestricted grant from Karolinska Institutet (No 2368/10-221, Distinguished Professor Award to SC). NR is supported by a postdoctoral fellowship award from the Canadian Institutes of Health Research. KSJ is supported by the BC Children’s Hospital Research Institute. Funders were not involved in the design and conduct of the study; collection, management, analysis, or interpretation of the data; and preparation, review, or approval of the manuscript.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: This study was approved by the regional ethic review board at Karolinska Institutet, Stockholm, Sweden (No 2018/1377-32).

  • Data sharing: No additional data available.

  • Transparency: The lead author (NR) affirms that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

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