Covariates adjusted for are described in the Statistical Analysis subsection of the Methods section. Fat mass index is calculated as fat mass divided by height in meters squared. Error bars represent 95% CIs. BMI indicates body mass index; CDC, Centers for Disease Control and Prevention; HOMA-IR, homeostasis model assessment of insulin resistance; PROBIT, Promotion of Breastfeeding Intervention Trial; WFL, weight for length; and WHO, World Health Organization.