Associations between Infant Growth and Later Outcomes: Does the Choice of Growth Reference Matter?

Background: Use of different infant growth references (GR) can alter apparent infant growth pattern, but the impact on associations between early growth and later outcomes is unknown.

Objectives: To examine whether the choice of GR influences (1) apparent infant growth patterns; and (2) associations with later anthropometry and body composition (BC).

Methods: Weight, height, BMI, waist circumference (WC)) and BC (four component model: fat mass (FM), fat free mass (FFM)) were measured in 209 healthy British children (mean (SD) 11.1 (3.5) yrs, 104 boys). Infant weight data were extracted from parent-held child records for birth, 3, 6 and 12wk, 6 and 12mo and converted to SDS using UK90 reference and WHO growth standards. ∆wtSDS using the two GRs were compared and associations between ∆weight 3-6wk and 0-12mo and later measurements were assessed, adjusting for confounders.

Results: ΔwtSDS calculated using UK90 and WHO were significantly different at all ages. UK90 ΔwtSDS 0-3wk was significantly 0. WHO SDS were significantly 0 for 12wk-6mo, 6-12mo and -12mo. In boys, ΔwtSDS 3-6wk was positively associated with later height, weight and FFM regardless of GR although associations were stronger for WHO than UK90 (eg. 0.65 WHO (p=0.02), 0.57 UK90 (p=0.04)). In girls, ΔwtSDS 3-6wk was positively associated with later FM and fat-free mass index (FMI) using both UK90 and WHO, and with weight, BMI, WC only using UK90; all associations were stronger using UK90 than WHO. ΔwtSDS birth-12mo in boys and girls was significantly associated with all later outcomes except FMI, with similar effect sizes using UK90 and WHO.

Conclusion: Differences in infant growth patterns as a result of using different GRs may influence apparent associations with later outcomes: effects may differ by gender and growth period. This should be considered by researchers.