In every pregnancy, a woman starts out with a 3-5% chance of having a baby with a birth defect. This is called her background risk. This sheet talks about whether exposure to chemotherapy may increase the risk for birth defects over that background risk. This information should not take the place of medical care and advice from your health care provider.

What is chemotherapy?

Chemotherapy is a term that describes the use of drugs to treat various types of cancer. It is one of the most widely used methods to treat cancer. When a chemotherapeutic drug is given orally or intravenously, it enters the bloodstream and circulates throughout the body. Other types of cancer treatment include surgery and radiation. Different combinations of the above three methods are used to improve cancer treatment.

How does chemotherapy work?

Cancer cells are different from normal cells in your body. Cancer cells multiply and grow fast, and sometimes they spread to other areas of your body. Chemotherapy tries to block cancer cell growth. Each drug has its own specific use, strengths, and side effects.

Will I be able to become pregnant after having chemotherapy?

When chemotherapeutic drugs affect the division of cancer cells, they also interfere with the division of normal cells, including those in the reproduction system. This may affect a woman’s ability to become pregnant. For most women, reproductive function may return to normal within months after chemotherapy has been completed. For some women, it may take several years. The degree of effect that these agents have on reproductive function varies from one drug to another. Some agents inhibit reproductive function completely and others have only a limited effect. In general, younger women are more likely to regain reproductive function than older women.

Some women choose a method of fertility preservation before starting chemotherapy. The most established option is the freezing and storing of fertilized eggs, but there are also other options. You can talk to your health care provider about whether fertility preservation is right for you.

I had chemotherapy as a child. I am now pregnant. Will my previous exposure to these drugs cause birth defects in my baby?

Probably not. So far there are no studies that indicate that exposure to chemotherapeutic agents in childhood increases the risk for birth defects in the children of women who later become pregnant.

If I need chemotherapy in early pregnancy, can it cause birth defects?

Yes, it can. While there have been case reports of healthy babies born to women who underwent chemotherapy during the first trimester, there is a potential risk for birth defects. The risk for birth defects to occur is greatest when the fetus is exposed to chemotherapy during the first trimester of pregnancy. This is because the first trimester is when many of the internal and external structures of the fetus are forming and cells are growing quickly. Since chemotherapeutic drugs interfere with cell growth and division, the fetus is most vulnerable during this period of time. Exposure to chemotherapeutic drugs during the first trimester may also increase the risk for miscarriage. Therefore, whenever possible, chemotherapy is avoided during the first trimester of pregnancy.

Are there any risks from chemotherapy later in pregnancy?

The risk for birth defects is less when chemotherapy is administered in the second or third trimester. With a few exceptions (such as the brain and the reproductive system), most fetal organ system development is completed by the beginning of the second trimester. However, exposure to chemotherapeutic drugs in the second and third trimester has been associated with a greater risk for premature birth, low birth weight, and a temporary reduction in some of the baby’s blood cells.

Are some chemotherapeutic drugs safer than others?

Yes. When the infants of women who underwent chemotherapy during pregnancy were examined, maternal treatment with certain drugs showed a stronger link with an increase in birth defects than others. Although no chemotherapeutic drug can be considered totally safe for use in pregnancy, certain drugs may be less likely to cause birth defects. In addition to the specific chemotherapeutic drug used for maternal therapy, factors such as the number of different medications used at the same time, how often and how long the medications are used, and when in pregnancy the medications are taken may also influence the outcome. Please call MotherToBaby at 1-866-626-6847 to speak with an information specialist about your specific treatment.

If I undergo chemotherapy while I am pregnant, can it have delayed adverse effects on my baby?

Since there are some theoretical concerns that delayed adverse effects could potentially occur following prenatal exposure to chemotherapeutic drugs, more research needs to be done in this area. Therefore, it is recommended that babies be monitored for normal growth and development during pregnancy and after delivery.

Is it safe to breastfeed my baby while I am having chemotherapy?

No, breastfeeding is not recommended while women are receiving chemotherapy. Although it is not known how much of these medications are secreted in breast milk, there could be serious side effects in the nursing infant. These side effects could include suppression of the immune system and an increased risk for cancer. Be sure to talk to your health care provider about all your choices for breastfeeding.

If the father of my child has undergone chemotherapy will this affect my pregnancy?

Men who are facing cancer treatments may wish to consider sperm banking (freezing and storing) before treatment. Sperm production is frequently affected during cancer treatment. Although sperm production may return to normal after chemotherapy, it is not guaranteed. In addition, damage to the structure of chromosomes in sperm may occur. It is believed that most of the damage is not permanent, but some studies have detected higher than normal levels of abnormal sperm for years after the end of chemotherapy. Although the data are limited, if sperm production resumes, it appears that a man’s treatment with chemotherapeutic agents prior to conception does not increase the risk of birth defects in future children.

In general, exposures that fathers have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures and Pregnancy at