Do Fertility Drugs Increase Your Risk of Getting Cancer?

In a study conducted by the National Cancer Institute, researchers looked at 8,431 women who sought treatment for infertility between 1965 and 1988. Using questionnaires or death records, they found that 39 of the women developed uterine cancer, more than you’d expect if you compared this to the general population. The researchers concluded that use of Clomid may have increased their risk of developing uterine cancer.

They found that the risk of uterine cancer increased if higher dosages were used and if the drug was taken for six months or more. Notably, they found that the risk of developing uterine cancer was even stronger if the women were obese or never became pregnant, with a combination of these two factors raising the risk even higher.

The problem with this research study is it didn’t take into account other potential risk factors for uterine cancer. Namely, if a woman never experiences pregnancy, her risk of cancer increases. Also, obesity is not only a risk factor for infertility, but it is also a risk factor for cancer.

It may not have been the fertility drugs at all, but instead, the increased incidence may be attributed to the reason behind the infertility itself, or any number of other factors not taken into account in this study. In fact, recent studies have found a possible connection between certain causes of infertility and an increased risk of cancer.

Other studies that have found a connection between fertility drug use and cancer risk have similar problems. Either they failed to take into account other risk factors, including infertility itself, or the study sizes were too small to be considered strong evidence.

A meta-analysis is a research study that gathers information from several studies and evaluates them together. The University of Ottawa conducted a meta-analysis to look into whether fertility drug use increased the risk of cancer, when compared to infertile women who were not treated. The analysis included the data collected by 10 different research studies, with information on women taking fertility drugs like Clomid, gonadotropins, human chorionic gonadotropin (hCG), and gonadotropin releasing hormone agonists (GnRH).

The researchers found that when comparing infertile women treated with fertility drugs, against infertile women who were not treated, those treated with fertility drugs were not at an increased risk of developing uterine cancer. Most interestingly, they did find that women who were treated seemed to have a lower incidence of ovarian cancer, when compared to infertile women who were not treated.

In another study, this one conducted by the Danish Cancer Society, researchers did a cohort study of 54,362 women with infertility. (A cohort study is when they look at a large group of people with similar circumstances, typically over a long period of time.) In this study, the researchers found no significant increase in risk for breast cancer after fertility drug use, specifically gonadotrophins, Clomid, hCG, or GnRH.

There are other studies that have found similar results.

The general consensus is that fertility drugs do not increase your risk for developing breast or uterine cancer. In addition, some studies have looked at fertility drug use and other kinds of cancers (thyroid and skin cancers, for example), and they have also found no significant increase in risk.

However, because infertility itself is a risk factor for cancer, follow up after an infertility diagnosis is important. Women with primary infertility, who never become pregnant and give birth; as well as women diagnosed with endometriosis, may particularly have an increased risk of developing cancer. PCOS, a common cause of infertility, is also known to come with an increased risk of developing endometrial cancer.

While more research should be done, for now, fertility drugs are off the hook.

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