Age at first full-term pregnancy and mammographic breast density in postmenopausal women: a systematic review

While mammographic breast density (MBD) is a well-established independent risk factor for breast cancer and age at first full-term pregnancy (FFTP) has been identified as a protective factor, there are very few high-quality studies that address the relationship between these two variables. The goal of this work was to generate a systematic review of published studies that addresses the association between age at FFTP and MBD based on objective mammographic findings in postmenopausal women. The English-language literature published with a cutoff date 31 August 2022 in the PubMed, EMBASE, Scopus, Web of Science, and Cochrane Library databases was searched using relevant keywords. The Newcastle-Ottawa Quality Assessment Scale was used to assess the quality of all relevant studies identified in this search. Our search yielded 12 original publications (including one conference abstract) that focused on the impact of age at FFTP on MBD in studies that objectively evaluated this condition in women without any form of breast pathology. Of these, six studies revealed a direct association between older age at FFTP and higher MBD in postmenopausal women. The remaining six studies reported either no relationship between these parameters or revealed an inverse association between MBD and older age at FFTP. We concluded that half of the currently-published findings supported an association between older age at FFTP and higher MBD. However, substantial heterogeneity between FFTP and MBD might be explained by different racial clusters, lacking specific information of other reproductive factors and differences in methodology utilized. The goal of this work was to examine whether age at FFTP is associated with MBD in postmenopausal women.