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Birth weight centiles and small for gestational age by sex and ethnicity for England and Wales
  1. Anna Freni-Sterrantino1,
  2. Priscilla Afoakwah2,
  3. Rachel B Smith3,
  4. Rebecca E Ghosh1,
  5. Anna Hansell4,5
  1. 1 School of Public Health, Epidemiology and Biostatistics, Small Area Health Statistics Unit (SAHSU), MRC-PHE Centre for Environment and Health, London, UK
  2. 2 Eye Unit, AngloGold Ashanti Health Foundation, Obuasi Municipal, Ashanti Region, Ghana
  3. 3 Department of Epidemiology and Biostatistics, Imperial College London School of Public Health, London, UK
  4. 4 School of Public Health, Epidemiology and Biostatistics, Small Area Health Statistics Unit, MRC-PHE Centre for Environment and Health, Imperial College London, London, UK
  5. 5 Centre for Environmental Health and Sustainability, University of Leicester, Leicester, UK
  1. Correspondence to Dr Anna Freni-Sterrantino, Department of Epidemiology and Biostatistics School of Public Health, Imperial College London, London W2 1PG, UK ; a.freni-sterrantino{at}


Objectives To construct UK ethnicity birth weight centiles (UK-EBWC) for gestational age and cut-offs for small for gestational age (SGA) for England and Wales and to evaluate the SGA misclassification using the UK centiles.

Design Analysis of national birth data.

Participants All live singleton births in England and Wales in 2006–2012, as recorded by the Office for National Statistics and birth registrations, linked with National Health Service into numbers for babies.

Main outcome measures Both sex-specific and ethnicity-sex-specific birth weight centiles for gestational age, and ethnicity-sex-specific SGA cut-offs. Centiles were computed using the generalised additive model for location, scale and shape.

Results Our sex-specific centiles performed well and showed an agreement between the expected and observed number of births below the centiles. The ethnicity-sex-specific centiles for Black and Asian presented lower values compared with the White centiles. Comparisons of sex-specific and ethnicity-sex-specific centiles shows that use of sex-specific centiles increases the SGA diagnosed cases by 50% for Asian, 30% for South Asian (Indian, Pakistani and Bangladeshi) and 20% for Black ethnicity.

Conclusions The centiles show important differences between ethnic groups, in particular the 10th centile used to define SGA. To account for these differences and to minimise misclassification of SGA, we recommend the use of customised birth weight centiles.

  • birth weight
  • ethnicity
  • small for gestational age
  • birth weight centiles
  • UK charts

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  • Contributors AFS drafted the paper and supervised the statistical analysis conducted by PA. All the authors provided intellectual input, interpreted the results and helped to revise the manuscript. All authors approved the final version of the manuscript and agreed to be accountable for all the aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. AFS is the guarantor of this paper.

  • Funding The UK Small Area Health Statistics Unit (SAHSU) is part of the MRC-PHE Centre for Environment and Health, which is supported by the Medical Research Council (MR/L01341X/1) and Public Health England (PHE). The research was funded/part funded by the National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Health Impact of Environmental Hazards at King’s College London in partnership with Public Health England (PHE) and Imperial College London.

  • Disclaimer The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR, the Department of Health and Social Care or Public Health England.

  • Competing interests None declared.

  • Ethics approval This study uses SAHSU data, covered by national research ethics approval from the London-South East National Research Ethics Committee—reference 17/LO/0846. Data access is covered by the Health Research Authority—Confidentiality Advisory Group under section 251 of the National Health Service Act 2006 and the Health Service (Control of Patient Information) Regulations 2002 HRA CAG reference: 14/CAG/1039. Identifiable information has only been used under strict data sharing agreements with the data providers. SAHSU does not have permission to supply data to third parties.

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

  • Patient consent for publication Not required.