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Member Research & Reports

Member Research & Reports

Columbia: Number and Timing of Pregnancies Influence Breast Cancer Risk for Women with BRCA Mutations

Researchers at Columbia University Mailman School of Public Health and the Institut National de la Santé et de la Recherche Médicale in Paris confirm the lower risk of breast cancer from multiple pregnancies and from breast feeding seen in average risk women extends to those at the highest risk of breast cancer, according to the largest prospective study of BRCA1 and BRCA2 mutations carriers to date. Women with BRCA1 mutations who had two, three or four or more full-term pregnancies were at 21 percent, 30 percent, and 50 percent decrease risk of breast cancer compared to women with a single full-term pregnancy. Breastfeeding also reduced risk in BRCA1 mutation carriers.  Results are published in the Journal of the National Cancer Institute Cancer Spectrum.

Women with BRCA2 mutations did not have a decrease in risk from multiple pregnancies except if they had four or more pregnancies.  Women with BRCA1 mutations who had only one full-term pregnancy were at an increased risk of breast cancer.

“Timing really matters 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,” said lead author Dr. Mary Beth Terry, professor of epidemiology at Columbia Mailman and the HIC Cancer Center.  

“Moreover, the hormonal upheaval that occurs during the first pregnancy may have a more or less important impact on the risk of breast cancer depending on whether the first pregnancy is at higher risk periods of life,“ said Dr. Nadine Andrieu, at the Institut.

The study followed 5,707 BRCA1 and 3,535 BRCA2 mutation carriers in a retrospective cohort and a prospective cohort of 2276 BRCA1 and 1610 BRCA2 mutation carriers.

Read about co-authors and funding.