BACKGROUND Reproductive period for women, begins at menarche and ends at menopause, which represented the total time period of exposure to cycling reproductive hormones. The potential associations between clinicopathological features and the exposure of cycling reproductive hormones has not been extensively studied. The retrospective study enrolled 14,731 patients diagnosed with invasive breast cancer was designed to evaluate factors associated with the reproductive period on breast cancer type and patient outcomes. MATERIAL AND METHODS 14, 731 female breast cancer (BC) patients from Western China Clinical Cooperation Group (WCCCG) between January 1, 2008 to December 31, 2017 were identified. Unconditional logistic regression was performed to assess the associations between clinicopathological features and menarche age, menopause age, and reproductive years. The differences in risk factors between lower and higher number of reproductive years (<35 and ³35 yrs) were examined with the chi-square test. RESULTS First, patients with late menarche age were more likely to present with tumors of higher histological grade and larger sizes. Second, the findings suggested a higher likelihood of smaller tumor sizes in postmenopausal patients with a greater length of reproductive years. Conversely, higher histological grade was associated with this group of patients, compared to their counterparts with shorter reproductive years. Third, in luminal breast cancer, patients with a greater length of reproductive years were more probably present larger tumor. CONCLUSIONS Our findings indicated that several clinicopathologic factors including tumor size and histological grade were associated with the length of reproductive years in patients diagnosed with breast cancer.