Abstract: The effect of parity on breast cancer risk has been well documented.Pregnancy is associated with a reduction in a women，s lifetime risk of developing breast cancer.It remains controversial whether parity affects breast cancer subtype and survival.Current research shows that fertility not only affects the incidence of breast cancer，but also affects the prognosis of breast cancer.On the basis of studies on pregnancy-associated breast cancer（PABC），foreign scholars have recently proposed the concept of the time since last birth to breast cancer diagnosis（TSBB），which found that breast cancer patients with TSBB < 5 years had poorer survival outcomes.It is suggested to strengthen postoperative adjuvant therapy for these patients.Some studies suggest that this is not an independent predictor of poor prognosis of breast cancer，but is related to the biological characteristics of the tumor itself.The effect of fertility on the prognosis of breast cancer patients is still controversial.

Key words: parity, breast cancer, pregnancyassociated breast cancer, time since last birth to breast cancer diagnosis, prognosis