Birth weight centiles and small for gestational age by sex and ethnicity for England and Wales.

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.