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Tamoxifen and Pregnancy -- Safe or Risky?

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Updated March 17, 2010

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Question: Tamoxifen and Pregnancy -- Safe or Risky?

Question: Can I Get Pregnant If I Take Tamoxifen? Is Pregnancy and Tamoxifen a Dangerous Combination?

"I have finished my chemotherapy and now my doctor says I have to take Tamoxifen for five years. I just want to ask if I'm taking these tablets can I get pregnant? I mean - is it bad if I get pregnant while taking Tamoxifen? Will Tamoxifen prevent pregnancy?" - Rose, About.com Reader

Answer:

Congratulations on being a survivor! For premenopausal women, taking Tamoxifen (Nolvadex) will prevent estrogen from helping estrogen receptor positive recur or develop. But Tamoxifen is not contraception. While chemo may temporarily reduce your fertility, having children after you recover from treatment may still be possible. However, don't start a pregnancy and take Tamoxifen at the same time. The same cautions apply to a similar drug - Faslodex (fulvestrant).

Here are some reasons to be careful:

Tamoxifen, Estrogen, and Your Reproductive System
While you are taking Tamoxifen, your ovaries will still function normally and you may produce eggs and estrogen at normal or above average rates. So it will be possible to become pregnant. 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. Once the ovaries are in overdrive, Tamoxifen is stopped and then conception can be attempted.

Don't Mix Tamoxifen and Pregnancy
Tamoxifen can hurt fertilized eggs (embryos) so don't take it if you are already pregnant. If you think you have become pregnant, stop taking Tamoxifen and contact your doctor right away. In lab studies on pregnant animals, Tamoxifen has caused birth defects, miscarriage, and prevented fertilized eggs from attaching to the wall of the uterus.

Play It Safe For a Season
Avoid becoming pregnant while you're taking Tamoxifen - but use non-hormonal methods. Tamoxifen and the birth control pill should never be taken together because the pill will prevent Tamoxifen from working properly. Try condoms, spermicide, or a diaphragm to prevent a pregnancy. Don't attempt conception until you have been off of Tamoxifen for at least two months. This allows time for the drug to pass out of your system.

A Baby, Maybe?
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 think about your future priorities. There are many paths to parenthood, and one may be right for you.

Sources:

Tamoxifen: Questions and Answers. National Cancer Institute. Reviewed: 03/17/2008.

Tamoxifen Drug Description. American Cancer Society.

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