BRCA1 and ovarian cancer: Although data assessing many additional potential modifiable risk factors did not reach statistical significance, possible associations with increased breast cancer risks were shown for oral contraceptive use (both for BRCA1 and BRCA2) and smoking (BRCA2), whereas decreased breast cancer risks were demonstrated with breastfeeding and late age at menarche (BRCA1), and decreased ovarian cancer risk with breastfeeding, tubal ligation (BRCA1) and oral contraceptives (BRCA1 and BRCA2) [17].