Background: Longitudinal studies examining the potential mediating roles of birth weight and breastfeeding duration on the pathways between maternal gestational weight gain (GWG) and offspring anthropometric outcomes are lacking.
Methods: We analyzed data from the mother-child pairs in the Infant Feeding Practices Study II (IFPS II) in late infancy (n=1548) and at the Year 6 Follow-up (n=1514) Study. Child anthropometrics included age- and sex-specific Z-scores for weight for age (WAZ), height /length for age, weight for height/length and body mass index (BMIZ). Structural equation models were used to estimate the total, direct and indirect effects of GWG on child anthropometrics through birth weight and breastfeeding duration.
Results: The total effect of GWG on offspring anthropometric outcomes was significant for WAZ (β=0.107, 95% confidence interval (CI): 0.052, 0.161) at late infancy and for WAZ (β=0.122, 95% CI: 0.066, 0.177) and BMIZ (β=0.120, 95% CI: 0.063, 0.178) at 6 years old. The direct effects of GWG on offspring's WAZ and BMIZ were observed only at 6 years old. The indirect effects of GWG through birth weight were significant on most of the offspring's anthropometric measures. Compared to breastfeeding duration, birth weight was a stronger mediator on the pathways between GWG and all proposed anthropometric measures both in late infancy and in early childhood. Longer duration of breastfeeding was inversely associated with all offspring anthropometric outcomes at late infancy but not with those outcomes at 6 years old.
Conclusions: Our findings suggest a stronger indirect rather than direct effect of GWG on children's anthropometric outcomes mainly through birth weight, independent of maternal sociodemographic and reproductive factors. Longer duration of breastfeeding might suppress the positive relationship between GWG, birth weight and anthropometric outcomes in late infancy but not among 6 years old.