['The association between exclusive breastfeeding duration and infant anemia is not clear.', 'This study aimed to assess the association of exclusive breastfeeding duration with risk of anemia in infants at 12 mo of age and in children aged 48-71 mo in mainland China.', 'Detailed breastfeeding information and anthropometric data were obtained for 65,256 children enrolled in the Jiaxing Birth Cohort at 1, 3, and 6 mo of age. Hemoglobin was measured in 25,549 children at 12 mo and in 32,770 children between the ages of 48 and 71 mo. Anemia was defined as hemoglobin concentrations <110 g/L in children aged <60 mo and <115 g/L in children aged ≥60 mo. The associations between exclusive breastfeeding duration and risk of anemia were assessed as adjusted ORs by using multiple logistic regression.', 'Overall anemia prevalences at 12 and 48-71 mo were 24.9% and 9.9%, respectively. Exclusive breastfeeding for ≥6 mo, but not for 3-5 mo, was significantly associated with a higher risk of anemia in infants at age 12 mo (OR: 1.15; 95% CI: 1.02, 1.29; P = 0.02) compared with exclusive breastfeeding for <3 mo. For young children aged 48-71 mo, this finding was only marginally significant (OR: 1.13; 95% CI: 0.99, 1.29; P = 0.08). Prolonged duration of exclusive breastfeeding was also significantly associated with decreased hemoglobin concentrations of -0.56 g/L (95% CI: -1.10, -0.03; P = 0.04) in infants and -0.99 g/L (95% CI: -1.44, -0.55; P < 0.001) in young children.'] Does prolonged Exclusive Breastfeeding Duration be Positively Associated with Risk of Anemia in Infants Aged 12 Months?