Maternal Health and Sociodemographic Characteristics Influence Infant Growth to 24 Months in the Tunza Mwana Cohort: A Prospective Cohort Study

Upstream pathways influencing child growth are complex. Weight-for-age z-score (WAZ) reflects both ponderal and linear growth and can identify children at high mortality risk. Using data from a prospective cohort of 326 mother-child pairs in Kenya, we evaluated whether associations between maternal exposures and child growth outcomes in early and later childhood. Growth trajectories were examined using locally weighted scatterplot smoothing and piecewise linear mixed-effect models with a knot at age 3 months. Poisson regression models examined associations between maternal characteristics and child underweight (WAZ < -2) and stunting (LAZ < -2) before and after 3 months. Mean WAZ increased to a peak at 3 months before declining steadily through 24 months. Lower maternal education (adjusted β aβ -0.18; 95% CI: -0.24, -0.13), household crowding (aβ -0.2; 95% CI: -0.28, -0.11), lower wealth quintile (aβ -0.04; 95% CI: -0.06, -0.02) and multiparity (aβ -0.16; 95% CI: -0.23, -0.1) were associated with lower monthly rate of change in WAZ prior to age 3 months. Younger maternal age was associated with an increased monthly rate of change in WAZ (aβ = 0.13; 95% CI: 0.08, 0.18) before 3 months and decreased monthly WAZ (aβ -0.02; 95% CI: -0.03, -0.01) after 3 months. Preterm birth was associated with increased risk of underweight in both periods (aRR 2.77; 95% CI: 1.39-5.50). Maternal mental health, intimate partner violence and adverse childhood experiences were not significantly associated with child growth. Maternal nutritional, socio-economic and household-level factors shape early growth, emphasising the need for cross-sectoral programs to support growth.