Fertility and Pregnancy During Breast Cancer Treatment: What to Know

Choosing the appropriate treatment for breast cancer is always a careful consideration depending on an individual’s personal factors. However, if a woman is of childbearing years, and is pregnant or hopes to become pregnant, that decision can become even more complex.

Some—but not all—therapies for breast cancer may affect fertility during and/or after treatments. Specifically, both hormone therapy and chemotherapy can affect fertility.

Hormone Therapy and Fertility

“Many of the anti-estrogen medications have menopausal symptoms as side effects,” says Amy Tiersten, MD, a hematologist and oncologist at Dubin Breast Center at Mount Sinai Hospital in New York City. “If that occurs during childbearing years, that is, of course, potentially devastating.”

Because of the temporary menopausal symptoms, hormone therapy may prevent ovulation and make a woman infertile, according to the American Cancer Society (ACS). After treatment, some women may regain fertility and have healthy pregnancies afterwards, while others might enter early menopause.

Unfortunately, “many of these women will go on to need five or 10 years of an anti-estrogen pill, during which they can’t carry a pregnancy because those drugs would be damaging to a fetus,” says Dr. Tiersten.

Certain medications may be able to help increase the chances of fertility after anti-estrogen therapy. Additionally, ongoing studies are analyzing the safety of interrupting hormone therapy to carry out a pregnancy, and then resuming the therapy—but the results of this are yet unknown.

If the woman is still of childbearing age after completing anti-estrogen therapy, studies show it is safe to become pregnant, and that the pregnancy will not increase the chance of breast cancer recurrence.

Chemotherapy and Fertility

There are many types of chemotherapy drugs, and many of them can damage a woman’s eggs, according to ACS. However, whether or not a chemotherapy drug permanently affects a woman’s fertility can vary based on her age, the drug doses, and the type of drug.

If a woman is undergoing chemotherapy for breast cancer and wants to preserve her fertility, she and her treatment team will likely choose from chemotherapy drugs with a low risk of damaging eggs.

Additionally, women should avoid getting pregnant during or immediately after chemotherapy, as it can cause birth defects. Since chemotherapy can also damage the eggs, it’s dangerous to get pregnant since a damaged egg can result in genetic problems for the baby. For this reason, it’s recommended to wait at least six months to become pregnant after finishing chemotherapy.

“There are techniques to harvest eggs and embryos prior to starting chemotherapy, allowing patients to carry pregnancies afterward,” says Dr. Tiersten. Afterwards, the woman can use the frozen eggs or embryo to become pregnant, or a surrogate mother can help.

“Treatment for breast cancer is scary, and I think that the role of the medical oncology team is really to demystify it and carefully explain what will be happening and what can be done to ameliorate certain side effects,” says Dr. Tiersten.