Prior pregnancy is associated with a reduced the risk of breast cancer in women older than 40 years who are carriers of BRCA1 or BRCA2 mutations - which are known to increase the likelihood of developing the disease - according to a report in the Journal of the National Cancer Institute.

Previous studies have shown an association between a reduced risk of breast cancer and prior pregnancy, young age at first childbirth, and breastfeeding in the general population, the authors explain.

Dr. Nadine Andrieu from Institut Curie, Paris, France and colleagues investigated whether these factors reduced the risk of breast cancer in women participating in the International BRCA1/2 Carrier Cohort Study, which includes most of the large population-based studies of women carriers of BRCA1 and BRCA2 mutations.

Overall, women with a prior pregnancy had a slightly lower risk of breast cancer than women who were never pregnant, the team found, but the difference was not statistically significant.

Among women who had been pregnant and were older than 40, however, each additional birth reduced the risk of breast cancer by an estimated 14 percent, the results indicate.

There was no association between breast cancer risk and ever having breast fed, and no association between duration of breastfeeding and breast cancer risk, the report indicates.

“Our data provide evidence that multiple full-term pregnancies are associated with a moderate reduction in the risk of breast cancer in BRCA1 and BRCA2 mutation carriers, which is evident only in women older than 40 years,” the authors conclude. “This decrease in breast cancer risk appears to be consistent with that found in the general population.”

SOURCE: Journal of the National Cancer Institute, April 2006.