In addition to the main association between a woman's own genotype and her breast cancer status, the family-based design of the present study allows us to address this hypothesis indirectly, by examining the association between maternal carrier status of CYP17 or CYP19 gene variants (that is, exposure in utero to an altered level of maternal estrogens) and breast cancer status in daughters. Here, CYP19A1 is linked to breast carcinoma.