Tamoxifen and Pregnancy Safety Issues

Tamoxifen, Reproduction, and Pregnancy Risks

A pregnant lady looks out of her kitchen window
Kelvin Murray/Stone/Getty Images

Tamoxifen may reduce the risk of breast cancer in women at risk, as well as reduce the risk of breast cancer recurrence in survivors, but is it safe to use tamoxifen in pregnancy? Since more people are aware of the impact of family history in the development of breast cancer, and now that genetic testing for risk factors such as BRCA mutations, this question has become much more important. What do you need to know if you are taking tamoxifen to reduce your risk (or risk of recurrence after breast cancer), but plan on becoming pregnant in the future? Are there problems if tamoxifen is taken in pregnancy, and from another angle, could the use of tamoxifen impact your future fertility?

Tamoxifen Dangers in Pregnancy

If you're reading these words it's likely that you, or someone you care about is taking or considering the use of tamoxifen. If you are being proactive to reduce your risk, that's wonderful. And if the tamoxifen is to prevent breast cancer recurrence, congratulations on being a survivor! That said, there are several things you should know if you are considering pregnancy while on tamoxifen.

Tamoxifen, unfortunately, is not a safe medication to take in pregnancy and should never be used. From studies looking at women who did mix tamoxifen and pregnancy, it's fairly clear that tamoxifen can increase the risk of congenital anomalies in the fetus (it has teratogenic effects). If you learn you are pregnant while taking tamoxifen, stop the drug right away and visit your doctor. While tamoxifen use is associated with a relatively high rate of severe birth defects, it is still more likely that a child exposed to tamoxifen in utero will be born normal and without any congenital anomalies.

In addition to the risk of birth defects, tamoxifen use is linked to an increased risk of miscarriage.

Tamoxifen and Fertility

Upon learning that tamoxifen and pregnancy don't mix, you're probably wondering about the future.  When you are finished taking Tamoxifen, will pregnancy be okay? Thankfully, after a wash out period of a few months off of tamoxifen, the risk of birth defects from Tamoxifen goes away. In addition, studies tell us that tamoxifen is not associated with an earlier age of menopause. In other words, tamoxifen is unlikely to accelerate the "normal" process of decreased fertility that comes with getting older.

Tamoxifen and Contraception

It's very important to use good non-hormonal forms of contraception while taking Tamoxifen. Methods of contraception such as birth control pills, contain estrogen and progesterone which can fuel the growth of breast cancer, potentially increasing the risk of a recurrence. For those who have an elevated risk of breast cancer, it's important to understand that while generally fairly safe, oral contraceptives may increase the risk of developing breast cancer.

Many doctors recommend a combination of two methods of contraception just to be safe while taking tamoxifen. This is especially true if you are using a form of non-hormonal contraception that has a relatively high failure rate, such as a diaphragm or spermicide alone. Using condoms along with these other methods can be helpful. An IUD is an option for some women, but isn't usually recommended for women who have not yet had a child and wish to in the future.

If a condom breaks, or the heat of the moment leads to lack of contraception, there are now emergency contraception options available. Since these medications, like oral contraceptives, contain female hormones, it's extremely important that you talk to your oncologist before using these.

Tamoxifen and Your Reproductive System

While chemotherapy may temporarily make you "menopausal," it's not uncommon for fertility to return even years after this treatment. You won't suddenly become menopausal on tamoxifen, unless you were already close to that point when you started treatment. On the contrary, infertility specialists sometimes prescribe high doses of tamoxifen to increase egg production in women with infertility. Once the ovaries are in "overdrive," tamoxifen is stopped and then conception can be attempted. 

Play It Safe for a Season

Using tamoxifen after treatment for breast cancer reduces the risk of recurrence by up to 50%, and increases the chance that you will be around in the future to enjoy your family. It can be hard to put childbearing on hold during this time, but for now, it's important to focus on your own health and well-being. If you're using tamoxifen, it's also important to be aware that there are medications which can interact with its metabolism, essentially making it as if you weren't taking the drug at all. Learn as much as you can in order to get the benefits you are sacrificing for. When you do really want to plan a pregnancy you should be off of tamoxifen for at least 2 months.This allows time for the drug to pass out of your system.

What If You Really Want a Baby Now?

If you want to become pregnant and feel that time is running out for your fertility, discuss your options with your doctor. It may be possible to take tamoxifen for less than five years and still get the benefit of this drug. Your doctor can review your diagnosis with you, and help you figure out the minimum amount of time you need to take it. Research has shown that pregnancy after breast cancer treatment does not significantly increase your chances of recurrence. Spend some time and effort recovering your health and thinking about your future priorities. There are many paths to parenthood, and one may be right for you.

If You're Just Starting Treatment

If you've recently been diagnosed, and before treatment, learn how cancer treatment can affect fertility, and what you can do to plan ahead.

Was this page helpful?

Article Sources