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Time of birth and risk of neonatal death at term: retrospective cohort study

BMJ 2010; 341 doi: (Published 15 July 2010) Cite this as: BMJ 2010;341:c3498
  1. Dharmintra Pasupathy, MRC/RCOG clinical research fellow1,
  2. Angela M Wood, lecturer2,
  3. Jill P Pell, Henry Mechan professor of public health3,
  4. Michael Fleming, statistician4,
  5. Gordon C S Smith, professor of obstetrics and gynaecology1
  1. 1Department of Obstetrics and Gynaecology, University of Cambridge, and NIHR Cambridge Comprehensive Biomedical Research Centre, Cambridge CB2 2SW
  2. 2Department of Public Health and Primary Care, University of Cambridge, Cambridge CB1 8RN
  3. 3Public Health Section, University of Glasgow, Glasgow G12 8TA
  4. 4Information Services Division, NHS National Services Scotland, Paisley PA3 2SJ
  1. Correspondence to: G C S Smith gcss2{at}
  • Accepted 26 April 2010


Objective To determine the effect of time and day of birth on the risk of neonatal death at term.

Design Population based retrospective cohort study.

Setting Data from the linked Scottish morbidity records, Stillbirth and Infant Death Survey, and birth certificate database of live births in Scotland, 1985-2004.

Subjects Liveborn term singletons with cephalic presentation. Perinatal deaths from congenital anomalies excluded. Final sample comprised 1 039 560 live births.

Main outcome measure All neonatal deaths (in the first four weeks of life) unrelated to congenital abnormality, plus a subgroup of deaths ascribed to intrapartum anoxia.

Results The risk of neonatal death was 4.2 per 10 000 during the normal working week (Monday to Friday, 0900-1700) and 5.6 per 10 000 at all other times (out of hours) (unadjusted odds ratio 1.3, 95% confidence interval 1.1 to 1.6). Adjustment for maternal characteristics had no material effect. The higher rate of death out of hours was because of an increased risk of death ascribed to intrapartum anoxia (adjusted odds ratio 1.7, 1.2 to 2.3). Though exclusion of elective caesarean deliveries attenuated the association between death ascribed to anoxia and delivery out of hours, a significant association persisted (adjusted odds ratio 1.5, 1.1 to 2.0). The attributable fraction of neonatal deaths ascribed to intrapartum anoxia associated with delivery out of hours was 26% (95% confidence interval 5% to 42%).

Conclusions Delivering an infant outside the normal working week was associated with an increased risk of neonatal death at term ascribed to intrapartum anoxia.


  • Contributors: DP, AMW, and GCSS formed the hypothesis and designed the study. MF did the linkage and extracted the data. DP, AMW, and GCSS performed the analysis and interpreted the results. DP and GCSS drafted the paper. All authors contributed to editing the draft for content and approved the final version of the paper. GCSS is guarantor.

  • Funding: DP was supported by the Medical Research Council and the Royal College of Obstetricians and Gynaecologists (Florence and William-Blair Bell Memorial Fellowship Fund) clinical research fellowship. His current affiliation is clinical lecturer in Maternal and Fetal Medicine in the Academic Department of Women’s Health, King’s College London. The funding source had no involvement in the design of the study and collection, analysis, and interpretation of the data.

  • Competing interest: All authors have completed the unified competing interest form at (available on request from the corresponding author) and declare (1) no financial support for the submitted work from anyone other than their  employer; (2) no financial relationships with commercial entities that might have an interest in the submitted work; (3) no spouses, partners, or children with relationships with commercial entities that might have an interest in the submitted work; and (4) no non-financial interests that may be relevant to the submitted work.

  • Ethical approval: This study was approved by the privacy advisory committee of the Information and Statistics Division of NHS Scotland. The chair of the Scotland A research ethics committee has stated that analysis of anonymised extracts of the linked data does not require separate ethical approval.

  • Data sharing: No additional data available.

  • Accepted 26 April 2010

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