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Breast cancer is hard to detect during pregnancy and some types are breast screening, including mammograms, are considered unsafe during pregnancy. Further, changes in breast tissue during pregnancy can make screening for cancer more difficult. For this reason, high-risk women are recommended to undergo their annual screening before becoming pregnant. Some high-risk women choose to have prophylactic mastectomy before becoming pregnant in order to avoid the challenges of breast screening. This is a very personal decision.
A research study by Steven Narod, MD and colleagues suggested that pregnancy may affect breast cancer risk in BRCA mutation carriers. The effects vary between women with BRCA1 mutations compared to women with BRCA2 mutations. In BRCA2 carriers, more pregnancies may be associated with higher breast cancer risk. However, the increased breast cancer risk is statistically significant only after four births. In BRCA1 carriers, more pregnancies may be associated with lower risk for breast cancer risk. The decreased risk was statistically significant for breast cancer only after four birth.
A study from Spain showed that pregnancy lowered the risk for breast cancer in women with a BRCA 1 or BRCA 2 mutation. The same study also suggested that pregnancy may lower the risk for ovarian cancer in BRCA 1 but not BRCA 2 mutation carriers.
Larger research studies are needed to better understand the effects of pregnancy on cancer risk in mutation carriers.