The MAL-ED cohort study: methods and lessons learned when assessing early child development and caregiving mediators in infants and young children in 8 low- and middle-income countries.

More epidemiological data are needed on risk and protective factors for child development. In The Etiology, Risk Factors and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health and Development (MAL-ED) cohort study, we assessed child development in a harmonious manner across 8 sites in Bangladesh, Brazil, India, Nepal, Pakistan, Peru, South Africa, and Tanzania. From birth to 24 months, development and language acquisition were assessed via the Bayley Scales of Infant and Toddler Development and a modified MacArthur Communicative Development Inventory. Other measures were infant temperament, the child's environment, maternal psychological adjustment, and maternal reasoning abilities. We developed standard operating procedures and used multiple techniques to ensure appropriate adaptation and quality assurance across the sites. Test adaptation required significant time and human resources but is essential for data quality; funders should support this step in future studies. At the end of this study, we will have a portfolio of culturally adapted instruments for child development studies with examination of psychometric properties of each tool used.