Background Height growth is an indicator of early life growth conditions and is associated with health in later life (including cardiovascular disease and some cancers). Cross-sectional research has shown that ethnic differences in height exist, however little is known about how children from different ethnic backgrounds grow throughout childhood. Using contemporary and UK-representative data, we investigated how childhood height trajectories differ by ethnicity and whether any differences are explained by early life factors.

Methods We used data from the Millennium Cohort Study (~18 000 children born 2000–2002) and included White, South Asian (Indian, Bangladeshi and Pakistani) and Black (Black African and Black Caribbean) singletons with height measured at least 1 time point (n=15,114). Mixed effects cubic growth models were applied to height measurements at ~3, 5, 7 and 11 years to estimate ethnic differences in height trajectories with and without adjustment for early life factors: parental height, prenatal factors (birth order, maternal smoking during pregnancy and age at childbirth), birthweight, and family socio-economic circumstances in infancy (maternal education, family income).

Results Compared to their White counterparts, Black boys and girls were taller at 3 years by 2.1 cm (95% CI: 1.4, 2.9) and 3.1 cm (2.42, 3.73) and subsequently grew at a faster rate on average by 0.24 cm/year (0.13, 0.35) and 0.31 cm/year (0.18, 0.44), respectively. Consequently, height differences at age 11 were much greater. No differences were found between South Asian and White boys. South Asian girls were marginally taller at 3 years by 0.5 cm (0.1, 0.9) but had a slightly slower growth rate between 3 and 11 years by −0.12 cm/year (−0.19,–0.05). Height differences at 3 years increased after adjustment of parental height and further adjustment of birthweight, possibly because ethnic minority children on average did not have taller parents and had a lower birthweight than White children. Adjustment for other early life factors did not alter these differences further.

Conclusion Our study is the first to investigate ethnic differences in childhood height growth of UK children. Black children were taller and grew faster than White children, and this was not explained by early life factors explored. Despite having shorter parents, South Asians had a similar growth trajectory to White children, suggesting a greater intergenerational gain for South Asians. Future research should examine whether the height advantage seen in Black children continues beyond age 11, and the potential health implications of rapid height gain (often accompanied by rapid weight gain).