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.
Bibliographical noteFunding Information:
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.
© Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.
- UK charts
- birth weight
- birth weight centiles
- small for gestational age