When it comes to physical traits, such as eye color or body type, women are well aware that these can be inherited from either parent—but not so many realize that a genetic risk for breast or ovarian cancer is as likely to be passed down from dad’s side of the family as from mom’s.

Most inherited genetic predispositions to breast and ovarian cancers are caused by mutations in the BRCA1 and BRCA2 genes, and men are just as likely as women to pass on these mutations to their children. Yet when researchers at Princess Margaret Hospital in Toronto examined records from their cancer clinic, they found that women were five times more likely to be referred for genetic counseling due to a maternal history than for their paternal line.

This has important implications — not only for women worried about their own health but also for fathers who want to be sure that their daughters are doing all that they can to protect themselves. I contacted Len Lichtenfeld, MD, deputy chief medical officer at the national office of the American Cancer Society in Atlanta, who stressed the importance of learning as much as possible about both parents’ family history. “Many fathers don’t realize that they can be carrying the gene for breast and ovarian cancer,” he said, adding the surprising news that many health-care providers don’t know this either!

Of the 700,000 women worldwide diagnosed with breast cancer each year, 5% to 10% have a genetic predisposition, usually a mutation in one of the BRCA genes. Women with these mutations have a high risk for breast and/or ovarian cancer (a 55% to 87% risk for breast cancer and a 20% to 44% risk for ovarian cancer). In a commentary on the study published in the The Lancet Oncology, the researchers point out that if doctors don’t ask about the medical history on the paternal side, women may not realize that they could be at high risk for breast or ovarian cancer, and that could prevent them from seeking genetic testing.

What you can do…

Dr. Lichtenfeld urges women to invest some time into learning their family medical history — from both sides of the family. Ask questions of your relatives, and follow through to get as much information as you can. Be alert to other cancers connected to breast cancer on your father’s side, such as colon and ovarian cancers. “As you get older and relatives pass away, you’ll find that the memory of the diseases they had and the causes of death disappear with them,” Dr. Lichtenfeld points out. “If you discover a history of breast or ovarian cancer, especially premenopausal, on either side of your family, it’s very important to get a consultation with an experienced genetic counselor who will discuss whether a test for the BRCA1 or BRCA2 mutation is appropriate and the implications of the results.”

To learn more about how to explore your family health history, go to the Web site for the Surgeon General’s Family Health History Initiative, www.hhs.gov/familyhistory. You will be able to create, store and share an electronic record — and keep it confidential — for free. It may be the best thing you’ve ever done for yourself — and your family.