Stunting is prevalent in South Asia and is rooted in poor growth in utero through 24 mo of age. We assessed nutritional status and growth as weight‐for‐length (WLZ) and length‐for‐age (LAZ) z‐scores at birth, 1, 3, 6, 12, and 24 mo in singleton infants born to mothers receiving iron‐folic acid in a randomized trial of antenatal micronutrient supplements. WLZ increased from birth (‐0.81 ± 1.08, n=10,707) to 3 mo (‐0.44 ± 1.15, n=12,079), before declining to 24 mo (‐1.35 ± 0.98, n=5,289). LAZ also improved from birth (‐1.64 ± 1.18, n=12,976) to 6 months (‐1.36 ± 1.09, n=8,405) before declining to lowest values at 24 mo (‐2.01 ± 1.00, n=5,301). By 1 mo, exclusive (EBF), predominant (PBF), partial (pBF), and no breast feeding (noBF) were related to WLZ and LAZ. At 3 mo, WLZ was 0.12 (95%CI: 0.05, 0.19), 0.18 (0.12, 0.24), and 0.75 (0.43, 1.09) lower, and LAZ 0.07 (0.02, 0.11), 0.18 (0.14, 0.22), and 0.81 (0.61, 1.00) lower, respectively, for PBF, pBF, and noBF compared to EBF infants in birth weight‐adjusted analyses (all P<0.01). By 6 mo, EBF conferred no benefit to LAZ relative to PBF or pBF. These patterns were unaffected by respiratory illness, diarrhea, or fever. Our data support the critical role of breast feeding in early life for children in rural Bangladesh, but show that by 6 mo EBF is inadequate to sustain relative anthropometric gains, supporting guidelines to introduce nutritious complementary foods in mid‐infancy.Grant Funding Source: Supported by the Bill and Melinda Gates Foundation Grant #614