It found that the women who were sisters and daughters of breast cancer patients and who used the birth control pill introduced before 1975, have a three times greater risk of breast cancer than women who also have a family history of the disease but never used the pill.

[Steven Narod], chair of breast cancer research at Sunnybrook and Women's College Health Sciences Centre, examined the Mayo Clinic study. He wouldn't suggest women stop taking the pill.

Narod, one of Canada's leading genetic researchers, helped discover BRCA1 and BRCA2 - two gene mutations that point to a greater hereditary risk of breast and ovarian cancer. Almost 1 in 50 Canadian women with breast cancer carries either gene mutation.