OBJECTIVES: We investigated the relative benefit of maternal multiple micronutrient (MMN) supplementation during pregnancy and until 3 months postpartum compared with iron/folic acid supplementation on child development at preschool age (42 months). METHODS: We assessed 487 children of mothers who participated in the Supplementation with Multiple Micronutrients Intervention Trial, a cluster-randomized trial in Indonesia, on tests adapted and validated in the local context measuring motor, language, visual attention/spatial, executive, and socioemotional abilities. Analysis was according to intention to treat. RESULTS: In children of undernourished mothers (mid-upper arm circumference