Credit: Jade Brookbank/Getty Images

Jade Brookbank/Getty Images In October, E! News co-anchor Giuliana Rancic announced that shed been diagnosed with breast cancer just as shed entered her third round of in vitro fertilization (IVF). This reopened a debate about the safety of fertility drugs: Could Rancics past fertility treatments have contributed to the development of her cancer?

What the experts say
Women who undergo fertility treatments, including IVF, take medications to stimulate their reproductive systems. As a result, they are exposed to high levels of estrogen, which the National Institute of Environmental Health Sciences lists as a known carcinogen. But based on current research, scientists say theres little cause for concern.

"There is no convincing evidence that taking fertility drugs raises your risk of developing breast cancer," says Jennifer Litton, MD, a breast medical oncologist at MD Anderson Cancer Center in Houston. A 2010 analysis of 23 studies did not find an increase in breast cancer risk for women on any fertility drugs. Meanwhile, a Swedish study from 2010 found that breast and cervical cancer rates were actually lower in women who had children via IVF compared with those who hadnt.

As for ovarian cancer, the issue is complicated by the fact that infertility itself is associated with a higher risk. "When you compare infertile women to the general population, they have a higher incidence of ovarian cancer, but not one that is caused by IVF," says Jamie Grifo, MD, program director of the NYU Fertility Center. A large Danish study published in 2009 found no association between fertility drugs and ovarian cancer. And while a Dutch study published last year found that women who did IVF had a slightly higher risk of "borderline ovarian tumors" (treatable growths that are rarely life-threatening) compared with infertile women who didnt undergo the treatment, there wasnt a significant difference in rates of invasive ovarian cancers.

"IVF has been around for 34 years," says Laurie McKenzie, MD, director of onco-fertility at Houston IVF. "If there was a significant uptick in cancer rates as a result of these treatments, it would have come to our attention by now."

Theres one caveat, Dr. Litton says: "If you had a preexisting breast cancer that you didnt know about, and if its the kind of tumor thats fed by estrogen, there is the potential that fertility treatment could worsen the cancer." But pregnancy could do the same thing—which is why Rancic says her doctor insisted on a mammogram before continuing her IVF cycle. "Fertility treatments raise hormone levels for a matter of days," Dr. Grifo points out. "Thats far less time than the heightened hormonal exposure in nine months of pregnancy."

The bottom line
Fertility medications dont raise your risk of breast cancer, though they may accelerate the growth of a preexisting breast cancer. The drugs have recently been linked to a very small increased risk for noninvasive ovarian tumors. But experts dont believe the dangers are significant enough to warrant extra screenings for women who have taken fertility drugs in the past.