Luo J, Chen X, Manson JE, et al. - Since breast cancer can potentially have prenatal origins, researchers assessed the risk of postmenopausal breast cancer in relation to birth weight, body mass index at four time points over 25-years of adulthood, focusing on if weight and height changes over the adult life course could be the mediators of the link between birth weight and risk of breast cancer. Participants were 70,397 postmenopausal women (aged 50-79 years) without breast cancer at enrollment (1993-1998). These women were followed up to 25 years. Self-reported birth weight and weights at ages 18, 35 and 50 were obtained. Lower risk of breast cancer was observed in relation to birth weight of less than 6 pounds vs birth weight of 6 to 8 pounds. There was no link between birth weight of 8 pounds or more and the risk of postmenopausal breast cancer. Increased risk of breast cancer was reported in relation to weight gain in adulthood, irrespective of time periods. Overall, findings revealed a link between lower birthweight and lower risk of postmenopausal breast cancer. Childhood or adolescent growth, especially adult height, was identified as a significant mediator of this reduction in risk. According to the findings, the key to breast cancer prevention is reaching and maintaining a healthy weight during adulthood.