Evidence is limited and conflicting about whether women who breastfeed their infants lose more weight than do women who do not breastfeed (25-27). Most of the women in those studies did not follow the current recommendations to exclusively breastfeed for 6 mo and then to continue breastfeeding for ≥6 more mo (28). Moreover, there is a reproducible, negative association between prepregnancy BMI and the duration of breastfeeding (29), and evidence is accumulating that obesity makes breastfeeding more difficult (30). Thus, it is possible that the lack of a consistent relation between breastfeeding and a reduction in PPWR has resulted from a combination of a pattern of breastfeeding that would not be expected to modify weight loss appreciably, low statistical power, or the poor quality of information about the intensity and duration of breastfeeding (or all 3 factors), as well as a complex association with prepregnancy BMI.