Fetal growth does not modify the relationship of infant weight gain with childhood adiposity and blood pressure in the Southampton women's survey

Background: Rapid infant weight gain is a risk factor for childhood obesity. This relationship may depend on whether infant weight gain is preceded by in-utero growth restriction. Aim: Examine whether fetal growth modifies the relationship between infant weight gain and childhood adiposity and blood pressure. Subjects and methods: 786 children in the Southampton Women's Survey. We related infant weight gain (weight at 2 years-birth weight) to body mass index (BMI), %body fat, trunk fat (kg), systolic (SBP) and diastolic blood pressure (DBP) at age 6-7 years. Mean estimated fetal weight (EFW) between 19-34 weeks and change in EFW (19-34 weeks) were added to models as effect modifiers. Results: Infant weight gain was positively associated with all childhood outcomes. We found no evidence that these effects were modified by fetal growth (p > .1 for all interaction terms). For example, a 1 standard deviation (SD) increase in infant weight gain was associated with an increase in BMI z-score of 0.51 (95% CI 0.37;0.64) when EFW-change was set at -2 SD-scores compared with an increase of 0.41 (95% CI 0.27;0.54, p((interaction))=.48) when set at 2 SD-scores. Conclusion: The documented adverse consequences of rapid infant weight gain may occur regardless of whether growth was constrained in-utero.