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Do Fertility Drugs Increase Cancer Risk?

fertility drugs

Women who use fertility drugs to help them get pregnant generally do not need to worry about an increased risk of cancer. However, a greater chance of developing some cancers does exist for certain women, and there are other adverse effects from fertility drugs of which patients should be aware.

Let’s look at the good news first. At the 30th Annual Meeting of the European Society of Human Reproduction and Embryology (ESHRE) in Germany, a US team of researchers reported on the conclusion of a 30-year follow-up study of the use of conventional fertility hormones and associated cancer risk. Although interim reports have been published over the term of the study, this is the first time a summary of the findings concerning three reproductive cancers—breast, endometrial, and ovarian—has been presented.

Women in the study used fertility drugs that stimulate ovulation, including clomiphene (the most frequently used substance until the early 1980s) and gonadotropins, which contain follicle stimulating hormone (FSH) alone or are combined with luteinizing hormone (LH) or human menopausal gonadotropin (hMG, a mixture of FSH and LH).

Both FSH and LH are normally produced by the pituitary gland during a woman’s menstrual cycle and stimulate the ovaries to create a single egg each month. Injectable FSH alone or with LH can result in many follicles (cysts that contain eggs).

Overall, the study included 12,193 women in the United States who were treated for infertility between 1965 and 1988. The follow-up period ended in 2010 and included information on cancer and deaths for a total of 9,892 women.

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Here’s what the researchers found:

  • 749 cases of breast cancer, 119 of endometrial cancer, and 85 of ovarian cancer
  • Use of clomiphene at any time during the study was associated with a significant increased risk of breast cancer only in women who had used the drug for 12 or more treatment cycles
  • Use of clomiphene was not associated with an increased risk of endometrial or ovarian cancer
  • No increased risk of cancer was seen among women who were treated with gonadotropins (often along with clomiphene), except among those who never got pregnant.
  • Overall, the 30-year study did not support a “strong relationship” between using fertility drugs and the development of reproductive cancers. However, the authors also pointed out that use of gonadotropins increased significantly after the mid-1980s, and so the results do not reflect that increased usage.

Therefore, further investigation is needed in this area.

Side effects of fertility drugs
Gonadotropins can cause abdominal and/or breast tenderness, bloating, headache, mood swings, retention of fluid, and weight gain. Other side effects and complications may include the following:

  • Ovarian hyperstimulation syndrome, characterized by fluid accumulation in the abdomen, swelling of the hands and legs, shortness of breath, nausea, vomiting, and enlarged ovaries. This syndrome can be mild in up to 20 percent of cycles, but in 1 percent it can be severe. In the latter case, hospitalization may be necessary.
  • Ectopic pregnancy, in which the fetus grows in a fallopian tube. Such pregnancies occur in up to 2 percent of women who don’t take gonadotropins, but the risk is slightly higher among those who do.
  • Ovarian twisting, in which the ovary becomes twisted and blood flow is interrupted. Surgery is necessary to untwist the ovary or possibly remove it

Women who take clomiphene may experience the following adverse reactions:

  • Abnormal uterine bleeding, flushing, nausea, vomiting, diarrhea, breast tenderness, blurry vision, headache, enlarged ovaries
  • Ovarian hyperstimulation syndrome
  • Increased risk of multiple births, which is associated with additional risks for women and their babies

For women who are struggling with infertility, the use of fertility drugs is a common treatment option. The findings of this latest study provide women with some good news regarding the risk of cancer when using these medications.

American Society of Reproductive Medicine
Long-term relationship of ovulation-stimulating drugs to breast and gynecologic cancers. Abstract O-192. ESHRE