Objective To test the hypothesis that consumption of infant formulas containing long-chain polyunsaturated fatty acids (LCPUFAs) by preterm infants would favourably influence growth, body composition and blood pressure (BP) at age 10 years.

Methods This was a follow-up study of a preterm cohort (<35 weeks and birth weight <2000 g) randomly assigned to unsupplemented or LCPUFA-supplemented formulas to 9 months post term. The setting was a research clinic at Yorkhill Hospital for Sick Children, Glasgow, UK. A total of 107 children aged 9–11 years who participated in the original randomised controlled trial (45% follow-up) took part. Main outcome measures were: (1) anthropometry, (2) body composition and (3) BP.

Results There were no differences in growth or BP between randomised groups for the whole cohort. However, girls who had received LCPUFA-supplemented formula were heavier (42.20 (SD 9.61) vs 36.94 (9.46) kg, p=0.05), had greater skin fold thicknesses (biceps 10.7 (3.3) vs 8.5 (3.6) mm, p=0.03; suprailiac 16.7 (8.2) vs 12.0 (7.5) mm, p=0.03) and higher BP (mean 82.2 (8.4) vs 78.1 (6.2) mm Hg, p=0.04: systolic 111.4 (10.1) vs 105.9 (9.0) mm Hg, p=0.04: diastolic 64.8 (8.4) vs 61.1 (5.4) mm Hg, p=0.05). Differences in weight SD score (0.85 (95% CI 0.13 to 1.58), p=0.02), Ln sum of skin fold thicknesses (0.27 (0.02 to 0.52), p=0.04) and BP (mean 4.6 mm Hg (0.43 to 8.84), p=0.03; systolic 6.1 (0.45 to 11.7), p=0.04) remained after adjustment for prerandomisation confounders. Differences in BP were not significant following adjustment for current weight.

Conclusions Girls born preterm and randomised to LCPUFA-supplemented formula showed increased weight, adiposity and BP at 9–11 years, which might have adverse consequences for later health. No effects were seen in boys. Long-term follow-up of other LCPUFA supplementation trials is required to further investigate this finding.