Risk of Breast Cancer in BRCA1 and BRCA2 Mutation Carriers Influenced By Pregnancy and Breastfeeding

By Eliana Rosenzweig

Research published on March 8th confirms that both breast feeding and multiple pregnancies can decrease the risk of breast cancer in women at average to high risk. Researchers at Columbia University Mailman School of Public Health and the Institut National de la Santé et de la Recherche Médicale in Paris conducted the largest prospective study of BRCA1 and BRCA2 mutation carriers, using data from 21 national or center based prospective follow-up studies and looking at nearly 8,000 women in total. Compared to women with single fun-term pregnancies, women with BRCA1 mutations with two, three, four, or more full-term pregnancies decreased risk of breast cancer by 21 percent, 30 percent, and 50 percent, respectively. Breastfeeding was found to reduce the risk of breast cancer in the carriers for BRCA1 gene as well. In contrast, for women with the BRCA2 gene, it was found that risk of breast cancer only decreased with four or more full-term pregnancies. In fact, this study confirmed that women with a single full-term pregnancy with the BRCA1 gene and women with less than four full-term pregnancies were actually at a higher risk of developing breast cancer.  

Lead author Mary Beth Terry, Professor of Epidemiology and Environmental Health Sciences at the Mailman School of Public Health, said, "What we have learned is that timing really matters for many risk factors and the dual effect of pregnancy we see in non-mutation carriers with a long term protection but short term increase following a pregnancy may not extend to all women with BRCA1 and BRCA2 mutations as the short-term increase and long-term protection may relate much more to the timing of when these pregnancies occur.”


Columbia University's Mailman School of Public Health. (2019, March 8). Number and timing of pregnancies influence breast cancer risk for women with BRCA1 or BRCA2 mutation: Risk of breast cancer declined for women with BRCA1 gene and more than one pregnancy. ScienceDaily. Retrieved March 10, 2019 from www.sciencedaily.com/releases/2019/03/190308133331.htm