Why does birthweight vary among ethnic groups in the UK? Findings from the Millennium Cohort Study.

BACKGROUND Birthweight varies according to ethnic group, but it is not clear why such differences exist. We examine the contribution of socioeconomic, maternal and behavioural factors to differences in mean birthweight and the prevalence of low birthweight across ethnic groups. METHODS Data from the nationally representative UK Millennium Cohort Study (n = 16,157) on White, Indian, Pakistani, Bangladeshi, Black Caribbean and Black African infants were analysed. Cohort members were born in 2000-02, and data on birthweight, maternal, infant, behavioural and socioeconomic factors were collected by home interviews. RESULTS Indian, Pakistani and Bangladeshi infants were 280-350 g lighter, and 2.5 times more likely to be low birthweight compared with White infants. Black Caribbean infants were 150 g and Black African infants 70 g lighter compared with White infants, and Black Caribbean and Black African infants were 60% more likely to be low birthweight compared with White infants. For Black Caribbean, Black African, Bangladeshi and Pakistani infants, socioeconomic factors were important in explaining birthweight differences and, for Indian and Bangladeshi infants, maternal and infant factors were important in explaining birthweight differences. CONCLUSION Future policies aimed at reducing inequalities in birthweight must pay attention to the different socioeconomic and culturally-related profiles of ethnic minority groups in the UK.