Pregnancy After Breast Cancer OK

March 30, 2001 -- Women surviving breast cancer don't do any worse if they get pregnant -- and may even do better than women who don't become pregnant.

A new U.S. study finds that women who become pregnant any time after they learn they have early-stage breast cancer do not die sooner than women who did not become pregnant. In fact, they were more likely to be alive five and 10 years after their cancer diagnosis. The findings, from researchers at Harvard's Dana-Farber Cancer Institute, are remarkably similar to earlier studies of women in the U.S., Sweden, Denmark, and Finland.

It did not matter whether the women actually carried the pregnancy to term. Women who had an abortion or a miscarriage did just as well as women who actually gave birth.

"Our conclusion is very reassuring -- there is no evidence that pregnancy following a diagnosis of breast cancer in any way elevates a woman's risk of cancer coming back," lead researcher Shari Gelber, MS, MSW, tells WebMD. "Given the fact that all studies have found a slightly protective role, we think either there is something going on hormonally or, more likely, there is a self-selection going on. It's been called 'the healthy-mother effect.'"

The healthy-mother effect is based on the theory that only the healthiest breast cancer survivors will be able to become pregnant.

Beth A. Mueller, DrPH, professor of epidemiology at the University of Washington in Seattle, co-authored an earlier U.S. study but did not participate in the Dana-Farber study. "For a woman who has had breast cancer to decide to become pregnant, she has to be healthier than a cancer patient who is not doing well," Mueller tells WebMD. "The healthy-mother effect is something we need to consider in interpreting these results. Is this effect strong enough to cover up a harmful effect of pregnancy on survival? I don't think that is the case. I think it is very likely that for these women, pregnancy probably doesn't have a strong effect on survival -- if there is any effect at all."

Gelber and co-workers tried very hard to match women who became pregnant with other healthy women. The 94 women with a pregnancy were all participants in the International Breast Cancer Study Group. Each woman was compared with two study participants who did not have a pregnancy.

Significant survival differences were discovered between the two groups. Five years after their cancer diagnosis, 92% of the women who became pregnant and 85% of the women who did not become pregnant were still alive. Ten years after cancer diagnosis, 86% of the women who had a pregnancy and 74% of the women who did not get pregnant were still living.

"That's reassuring news for young women with breast cancer," Mueller says.

Gelber's team now is enrolling breast cancer patients aged 40 years and younger in a new trial. This time, instead of looking back at medical records, the researchers will follow the women from the time of their breast cancer diagnosis to study the effects of pregnancy.

"It won't resolve these issues exactly, but we'll collect information about the desire for pregnancy and what women who have had breast cancer are doing to achieve a pregnancy," Gelber says. "Another interesting question we will ask is what are women doing to preserve their ability to achieve pregnancy when they are faced with cancer therapy. There are some chemotherapies that are safer for a woman's ovaries -- and there is also some interest in freezing fertilized eggs for later reimplantation."