WEDNESDAY, April 19 (HealthDay News) -- Women over 40 years old who carry BRCA1 or BRCA2 mutations predisposing them to breast cancer have a 14 percent reduced risk of breast cancer with each full-term pregnancy, similar to the general population, according to a study in the April 19 issue of the Journal of the National Cancer Institute.
Nadine Andrieu, Ph.D., of the Institut Curie in Paris, France, and colleagues retrospectively examined breast cancer risk and pregnancy in 1,601 European and Canadian women who were carriers of a BRCA1 or BRCA2 mutation, of whom 853 had breast cancer. The women had provided information on childbirth history, age at time of pregnancy and breast-feeding habits through a questionnaire.
The researchers found a significant 14 percent reduction in breast cancer risk with each full-term pregnancy in women over 40 years old, regardless of which gene was mutated. In BRCA2 carriers, breast cancer risk increased with increasing age at first childbirth, with a hazard ratio of 1.97 for women who were 30 years or older at first childbirth compared with women who were 20 years or younger. In contrast, BRCA1 carriers who were 30 years or older at first childbirth had a reduced breast cancer risk compared with women who were 20 years or younger at first childbirth (hazard ratio 0.58).
"In conclusion, 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," Andrieu and colleagues write. "This decrease in breast cancer risk appears to be consistent with that found in the general population."