AIM: Exclusive breastfeeding (EBF) for 6 months is recommended for optimal infant health, but the evidence for longer-term impacts is weak. We examined whether randomization to receive EBF counselling (BFC) in rural Bangladeshi women had an impact on childhood growth trajectories and body composition. METHODS: In the Maternal and Infant Nutrition Interventions in Matlab trial, 4436 pregnant women were randomized to six equally sized, food and micronutrient groups. Of these, 3214 were randomized during the last trimester of pregnancy to receive either BFC or the usual/standard health message (UHM). Their infants were extensively followed up, with anthropometric measurements between 0 and 54 months and assessment of body composition at 54 months. RESULTS: The mean duration of EBF in the BFC group was 111 days compared to 76 days in the UHM group (mean difference: 35.0 days, 95% CI 30.6-39.5, p < 0.001). There was no difference in growth trajectories between the BFC and UHM groups and no difference in body composition at 54 months. Children exposed to prenatal multiple micronutrients (vs 60 mg iron and folate) combined with BFC (vs UHM), however, had slower linear growth (mean difference -0.17 SD score, p < 0.01). CONCLUSION: Exclusive breastfeeding counselling resulted in neither differential growth trajectories in infancy and childhood, nor body composition differences at 54 months. The combination of prenatal multiple micronutrient supplementation (MMS) and BFC was unfavourable for linear growth during 0-54 months, which raises questions about possible negative effects of MMS.