The information provided below is for readers based in the United States of America. Readers outside of the United States of America should seek the information from local sources.


Trastuzumab is expected to cause fetal harm and should not be used during pregnancy or while breastfeeding.

What is trastuzumab?

Trastuzumab is a toxic medication used to treat breast cancer.

What is trastuzumab used to treat?

Trastuzumab is a prescription medication used to treat human epidermal growth factor receptor 2 (HER-2) positive breast cancer that has spread within the body, stomach cancer, and esophageal cancer. This medication may be used in combination with other medications such as paclitaxel.

How does trastuzumab work?

Trastuzumab is an antibody that binds to the HER-2 receptors in cancerous cells that have a high number of these receptors, leading to death of cancerous cells.

If I am taking trastuzumab, can it harm my baby?

It is unknown if trastuzumab human placenta to reach the developing baby. Only 6 case reports of women who took trastuzumab during pregnancy are available. Three of the six women stopped trastuzumab during the first trimester. No birth defects were identified in the six births; however, toxic effects on the kidneys have been reported due to low or deficient amniotic fluid levels in the mother with second and third trimester exposure to the medication. Maternal discontinuation of trastuzumab reversed any kidney damage that was reported in these cases. Other side effects in the baby due to low amniotic fluid levels include underdevelopment of the lungs, abnormal skeletal development, and death. Further studies are needed to understand the risks of this medication to the developing baby. HER-2 receptors are present within the baby's tissues and blocking these receptors with trastuzumab may be harmful for the baby's development. Trastuzumab may improve the pregnancy outcome, but it is generally recommended to avoid this medication while pregnant unless it is required.

If I am taking trastuzumab and become pregnant, what should I do?

It is recommended to use contraception to avoid pregnancy while on trastuzumab therapy and for at least 7 months after stopping therapy. Pregnancy testing is performed in women before to starting this medication. If trastuzumab therapy is required during pregnancy, the woman must be advised on the safety risks. European guidelines and some studies recommend delaying trastuzumab therapy until after pregnancy in women with HER-2 positive breast cancer who become pregnancy while on this medication. Women on this medication during pregnancy will be monitored and the baby's development will also be monitored. The manufacturer of trastuzumab maintains records on pregnancy exposure to the medication.

If I am taking trastuzumab, can I safely breastfeed my baby?

Breastfeeding should be avoided while taking this medication and for at least 7 months after stopping this medication. Although the effects of trastuzumab exposure in breastfeeding infants is unknown, adult side effects with trastuzumab therapy include heart dysfunction/failure, diarrhea, anemia, and decreased white blood cell counts with increased infection risk.

If I am taking trastuzumab, will it be more difficult to get pregnant?

Animal studies have not identified any impairments in fertility with trastuzumab.

If I am taking trastuzumab, what should I know?

Trastuzumab is a toxic anticancer medication that should be avoided during pregnancy and breastfeeding to prevent side effects in the baby.

If I am taking any medication, what should I know?

This report provides a summary of available information about the use of HER-2 receptor inhibitors during pregnancy and breastfeeding. Content is from the product label unless otherwise indicated.

You may find Pregistry's expert reports about oncology here,  reports about the individual medications used to treat cancer here, and a report about cancer here. Additional information can also be found in the resources below. 

For more information about trastuzumab during and after pregnancy, contact http://www.womenshealth.gov/ (800-994-9662 [TDD: 888-220-5446]) or check the following link:

Gene.com: Herceptin Prescribing Information

Read the whole report
General information

It is very common for women to worry about having a miscarriage or giving birth to a child with a birth defect while they are pregnant. Many decisions that women make about their health during pregnancy are made with these concerns in mind.

For many women these concerns are very real. As many as 1 in 5 pregnancies end in a miscarriage, and 1 in 33 babies are born with a birth defect. These rates are considered the background population risk, which means they do not take into consideration anything about the health of the mom, the medications she is taking, or the family history of the mom or the baby’s dad. A number of different things can increase these risks, including taking certain medications during pregnancy.

It is known that most medications, including over-the-counter medications, taken during pregnancy do get passed on to the baby. Fortunately, most medicines are not harmful to the baby and can be safely taken during pregnancy. But there are some that are known to be harmful to a baby’s normal development and growth, especially when they are taken during certain times of the pregnancy. Because of this, it is important to talk with your doctor or midwife about any medications you are taking, ideally before you even try to get pregnant.

If a doctor other than the one caring for your pregnancy recommends that you start a new medicine while you are pregnant, it is important that you let them know you are pregnant.

If you do need to take a new medication while pregnant, it is important to discuss the possible risks the medicine may pose on your pregnancy with your doctor or midwife. They can help you understand the benefits and the risks of taking the medicine.

Ultimately, the decision to start, stop, or change medications during pregnancy is up to you to make, along with input from your doctor or midwife. If you do take medications during pregnancy, be sure to keep track of all the medications you are taking.