Suboptimal growth is apparent across generations. Gestational weight gain (GWG) and infant feeding have been linked to child growth trajectories. This study assessed the joint association of GWG and infant feeding with three growth outcomes: length, weight, and weight-for-length.

I analyzed data from the Infant Feeding Practices Study II (2007), a nationally-based sample of mother/infant dyads followed from the third trimester of pregnancy through infancy (N=1939). GWG was defined as inadequate, adequate, and excessive. Predominant feeding categories were defined as ≥ 70% breast fed, ≥ 70% formula fed, and mixed fed. Linear multiple regression and mixed effect models were fit to achieve the study aims.

At three months, compared to the adequate GWG group, the inadequate group were lighter (-0.24 lbs.; 95% CI: -0.36, -0.12) and shorter (-0.13 in.; 95% CI: -0.23, -0.03), while the excessive group was heavier (0.28 lbs.; CI: 0.19, 0.38) and longer (0.09 in.; 95% CI: 0.01, 0.17). At five months, compared to breastfed infants, formula fed infants were heavier (0.38 lbs.; 95% CI: 0.26, 0.50); and the association between feeding type and length was apparent at seven months, where formula fed were longer (0.24 in.; 95% CI: 0.10, 0.39). An association between feeding type and weight-for-length was evident at twelve months, where the ratio for formula fed was greater (0.03 lbs./in.; 95% CI: 0.03, 0.04). The weight gain trajectory of breastfed infants was lower than the other feeding groups. The length trajectories were highest among formula fed compared to breastfed and mixed fed infants. The interaction between GWG and feeding type was significant for weight (p<0.05) and marginally significant for length (p=0.06).

My findings suggest existence of a difference in growth by GWG and feeding type. The weight trajectory of breastfed infants is steadier than that of other infants, highlighting the protective effect of breastfeeding on excessive weight gain. The growth rate for all feeding groups was fastest between 3-5 months, suggesting a critical window for growth during early infancy. Interventions targeting pregnancy and infancy can influence growth trajectories and contribute to a shift in intergenerational population growth trends.