The Effects of Breastfeeding Exclusivity on Early Childhood Outcomes

Objectives. We examined the relationship between breastfeeding exclusivity and duration and children’s health and cognitive outcomes at ages 2 and 4 years.Methods. We used the Early Childhood Longitudinal Study—Birth Cohort, a nationally representative sample of 10 700 children born in the United States in 2001. Parent interviews and child assessments were conducted in measurement waves at 9 months, 2 years, 4 years, and in kindergarten, with the focus on ages 2 and 4 years. We employed propensity scores as a means of adjusting for confounding involving observed characteristics.Results. Outcome analyses using propensity scores showed some small effects of breastfeeding on key outcomes at age 4 years but not at age 2 years. Effects appeared to be concentrated in reading and cognitive outcomes. Overall, we found no consistent evidence for dosage effects of breastfeeding exclusivity. Our sensitivity analyses revealed that a small amount of unobserved confounding could be responsible for the resulting benefit...