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Effects of gestational age at birth on health outcomes at 3 and 5 years of age: population based cohort study

BMJ 2012; 344 doi: (Published 01 March 2012) Cite this as: BMJ 2012;344:e896
  1. Elaine M Boyle, senior lecturer in neonatal medicine1,
  2. Gry Poulsen, researcher in statistics and epidemiology2,
  3. David J Field, professor of neonatal medicine1,
  4. Jennifer J Kurinczuk, director2,
  5. Dieter Wolke, professor of developmental psychology and individual differences3,
  6. Zarko Alfirevic, head of women’s and children’s health4,
  7. Maria A Quigley, reader in statistical epidemiology2
  1. 1Department of Health Sciences, University of Leicester, Leicester LE1 6TP, UK
  2. 2National Perinatal Epidemiology Unit, University of Oxford, Oxford OX3 7LF, UK
  3. 3University of Warwick, Department of Psychology and Division of Mental Health and Wellbeing, Warwick Medical School, Coventry CV4 7AL, UK
  4. 4University of Liverpool, Department of Women’s and Children’s Health, Institute of Translational Medicine, Liverpool Women’s Hospital, Liverpool L8 7SS, UK
  1. Correspondence to: E M Boyle eb124{at}
  • Accepted 5 December 2011


Objective To investigate the burden of later disease associated with moderate/late preterm (32-36 weeks) and early term (37-38 weeks) birth.

Design Secondary analysis of data from the Millennium Cohort Study (MCS).

Setting Longitudinal study of infants born in the United Kingdom between 2000 and 2002.

Participants 18 818 infants participated in the MCS. Effects of gestational age at birth on health outcomes at 3 (n=14 273) and 5 years (n=14 056) of age were analysed.

Main outcome measures Growth, hospital admissions, longstanding illness/disability, wheezing/asthma, use of prescribed drugs, and parental rating of their children’s health.

Results Measures of general health, hospital admissions, and longstanding illness showed a gradient of increasing risk of poorer outcome with decreasing gestation, suggesting a “dose-response” effect of prematurity. The greatest contribution to disease burden at 3 and 5 years was in children born late/moderate preterm or early term. Population attributable fractions for having at least three hospital admissions between 9 months and 5 years were 5.7% (95% confidence interval 2.0% to 10.0%) for birth at 32-36 weeks and 7.2% (1.4% to 13.6%) for birth at 37-38 weeks, compared with 3.8% (1.3% to 6.5%) for children born very preterm (<32 weeks). Similarly, 2.7% (1.1% to 4.3%), 5.4% (2.4% to 8.6%), and 5.4% (0.7% to 10.5%) of limiting longstanding illness at 5 years were attributed to very preterm birth, moderate/late preterm birth, and early term birth.

Conclusions These results suggest that health outcomes of moderate/late preterm and early term babies are worse than those of full term babies. Additional research should quantify how much of the effect is due to maternal/fetal complications rather than prematurity itself. Irrespective of the reason for preterm birth, large numbers of these babies present a greater burden on public health services than very preterm babies.


  • Contributors: All authors contributed to the design of the study. GP and MAQ did the data analysis. All authors interpreted the results. EMB, DJF, and GP drafted the paper. JJK, DW, ZA, and MAQ reviewed and edited the paper. MAQ is the guarantor.

  • Funding: The BUPA Foundation funded the study but had no role in the study design, data analysis and interpretation, or writing of the report.

  • Competing interests: All authors have completed the Unified Competing Interest form at (available on request from the corresponding author) 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 research involved secondary analysis of the Millennium Cohort Study and therefore did not require ethical approval. The multi-centre research ethics committee granted ethical approval for the MCS.

  • Data sharing: The datasets are available on the UK Data Archive. Further information about the study and data can be found at

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