Prognostic influence of pregnancy before, around, and after diagnosis of breast cancer.

A woman's risk of developing breast cancer is closely related to reproductive factors. Whereas the etiological importance of reproductive factors is well described, less is known about the prognostic influence of these factors. The prognostic effect of childbearing before, around, and after diagnosis is reviewed based on the literature and on studies from Danish Breast Cancer Cooperative Group, DBCG. In women with breast cancer overall number of childbirths is found to be without prognostic importance. Women with early primary childbirth seem to have an inferior prognosis compared to women who postpone childbearing. It is generally accepted that early first childbirth is associated with reduced risk of developing breast cancer. Thus, it is proposed that women who develop breast cancer despite an early first delivery represent a selected group of patients with particularly aggressive disease. Women diagnosed with breast cancer during pregnancy often present with advanced disease, but pregnancy at time of diagnosis does not seem to be an independent prognostic factor. However, women diagnosed with breast cancer in the first years after childbirth have a significantly reduced survival. It is assumed that these women, due to the physiological changes during pregnancy, experience growth induction of the tumours during the preclinical stage. In contrast, there is no evidence that pregnancy after breast cancer treatment has a negative influence on prognosis.