Prenatal and postnatal environmental influences on child growth trajectories across a rural-urban gradient: an analysis of the ECoMiD longitudinal birth cohort.

Background: Early childhood growth, a key indicator of child well-being, is shaped by both the prenatal and postnatal environment. To understand where and when environmental factors influence growth most, we analyzed size at birth, postnatal growth trajectories, and associations with environmental factors across a rural-urban gradient in the ECoMiD longitudinal birth cohort. Methods and Findings: Between 2021-2022, pregnant women were enrolled from four sites in northwest coastal Ecuador (urban city, intermediate town, rural villages connected by road, rural villages connected by river) and children were visited shortly after birth and quarterly thereafter for 24 months. We selected exposure variables using UNICEF's Conceptual Framework on Maternal and Child Malnutrition, including demographics, maternal characteristics, household infrastructure, and environmental factors. We used multivariable linear models and generalized estimating equations to analyze associations between exposures and length-for-gestational-age Z-score (LGAZ) and postnatal change in 3-month length-for-age Z-score (3-month ΔLAZ) and explored effect measure modification by site and child age (0-6 versus 7-24 months). Among 401 children, LGAZ was higher among children born to taller mothers, in households with higher food security, and in the rural river site. However, the postnatal growth of children in rural river sites faltered most rapidly, particularly after six months, resulting in 51% of children stunted (LAZ < -2 SD) at 24 months, compared to urban (8%), intermediate (14%), rural road (5%). Over the 0-24 month postnatal period, 3-month ΔLAZ was negatively associated with children who were male, from poorer households, had shorter mothers, and had greater exposure to animals and animal feces. Other associations, including with season, hygiene characteristics, and maternal demographics, varied by age and site. Conclusions: These findings show that environmental conditions influenced postnatal linear growth more strongly, compared to prenatal growth, which was associated with maternal anthropometry and nutrition. Community context strongly influenced growth only after age six months and modified associations with environmental conditions, suggesting that interventions targeting child growth faltering after six months may be important for certain populations.