AIMS To investigate the relation between haemoglobin in children followed longitudinally from 8 to 18 months, and developmental outcome at 18 months.

RESULTS There was a strong quadratic association between Hb at 8 months and performance on the locomotor subscale at 18 months. Average scores increased with increasing Hb up to 95 g/l; there was little additional developmental benefit in Hb levels beyond 95 g/l. Infants with Hb <95 g/l at 8 months of age scored on average 6 points lower on the locomotor subscale than infants with Hb ⩾ 95 g/l; infants with Hb <90 g/l at 8 months scored 12 points lower on the locomotor subscale than children with Hb ⩾ 90 g/l.

CONCLUSIONS Low Hb concentrations (⩽ 95 g/l) in 8 month old children are associated with impaired motor development at 18 months. This cut off point corresponds to the 5th centile of Hb at 8 months. The results indicate that if there is an adverse effect of low Hb on developmental outcome, screening may be more effective at 8 months or earlier, rather than after this age. We propose to examine the importance of infant anaemia in relation to more accurate and detailed long term outcomes as the children get older.