Cancer during pregnancy

Last medical review:

Cancer during pregnancy is rare. Because it's rare, not a lot of research has been done on it so not a lot of information is available. Making decisions that are right for you can be hard. There are many issues to consider.

You may worry that cancer, its treatment and the tests to diagnose cancer will affect the well-being of your baby.

Some cancer treatments are safe for the baby during pregnancy or during certain times of the pregnancy. Others are not safe for the baby at any time. Most cancers do not spread from a woman to the baby. Recent improvements in treatments and careful monitoring provide safer conditions for pregnant women with cancer so that it is more likely that the baby will be successfully delivered with good outcomes. It is important to know that if you are pregnant and living with cancer you can still give birth to a healthy baby.

Types of cancer

Pregnancy itself does not cause cancer and being pregnant does not increase the risk of developing cancer.

The most common cancers diagnosed during pregnancy include:

  • breast (the most common)
  • cervical
  • Hodgkin lymphoma
  • non-Hodgkin lymphoma
  • ovarian
  • melanoma skin cancer
  • leukemia
  • thyroid
  • colorectal

In very rare cases, cancer may develop from a molar pregnancy. Molar pregnancies are a type of gestational trophoblastic disease. The tissue that normally becomes a fetus instead becomes an abnormal growth in the uterus. A molar pregnancy can cause the same symptoms as pregnancy, but it is not a normal pregnancy. A fetus does not form from a molar pregnancy.

Find out more about gestational trophoblastic disease.

Diagnosing cancer during pregnancy

Many symptoms such as nausea, vomiting, abdominal bloating, breast changes (lumps), rectal bleeding, fatigue and headaches are common during pregnancy. But sometimes these symptoms can also be related to a specific type of cancer. It is important to talk with your doctor about symptoms if they continue or happen at a time during the pregnancy when it is no longer considered typical.

Sometimes pregnancy can uncover cancer earlier than it would otherwise have been found. For example, a Pap test done as part of routine care during pregnancy can find cervical cancer. An ultrasound done during pregnancy may find ovarian cancer.

If cancer is suspected, you may worry about using tests to diagnose cancer because of potential harm to the baby. For example, you may be worried about the radiation exposure during x-rays, CT scans or nuclear medicine tests. But some of these tests can be used safely during pregnancy, giving your doctor extra information to best treat the cancer.

X-ray and CT scan

Whether these tests cause harm to the baby depends on the stage of pregnancy, the number and type of x-rays used and the amount of radiation used. A lead shield is always used to cover the mother's abdomen for extra protection during both x-rays and CT scans.

Research has shown that the level of radiation in an x-ray (with appropriate shielding) used to diagnose cancer is too low to harm the baby.

CT scans use a higher level of radiation than routine x-rays and are much more accurate at showing internal organs and structures. They can help diagnose cancer or see if and where the cancer has spread. CT scans to the head and chest are usually safe. But CT scans to the abdomen or pelvis should only be done if absolutely necessary to plan your treatment.

MRI, ultrasound and biopsy

MRIs and ultrasounds are considered safe during pregnancy because they do not use radiation. Physical exams and many biopsies are also safe and important tools to diagnose cancer. If you are worried about a particular test, talk to your doctor.

Cancer treatment during pregnancy

Treating cancer during pregnancy is very complex. Before being treated for cancer and throughout the pregnancy, your pregnancy doctor (called an obstetrician) will assess the age of the baby, physical maturity of the baby and expected delivery date to help plan your treatment and make sure the baby is growing properly.

The healthcare team will look at the best treatment options for you, balancing them with possible risks to the baby. The cancer treatment options when you're pregnant are the same as the options for people who aren't pregnant, but how and when the treatment is given may be different.

The type of treatment and when it may be given depends on many things including:

  • the location of the cancer
  • the type of cancer
  • the stage of the cancer
  • the age of the baby (how long you have been pregnant)
  • how urgently treatment is needed
  • what you prefer or want

Treatment is tailored to you. Cancer treatments used during pregnancy include surgery, chemotherapy and sometimes radiation therapy, but these are only used after careful thought and planning to improve your health and the health of your baby.

Some cancer treatments can harm a baby, especially during the first 3 months of pregnancy, called the first trimester. This is when the baby develops its body structure and organs. Sometimes cancer treatment may be delayed until later in the pregnancy, during the second or third trimester.

When cancer is diagnosed later in a pregnancy, it may be possible to wait to start treatment until after the baby is born. The doctor may also consider inducing, or bringing on, labour early.

For some very early stage cancers, such as very early stage cervical cancer, it may be safe to continue the pregnancy to term and delay treatment until after the baby is born. Or minor surgery to treat cancer in its early stage can be safely done without harming the baby.

In some situations, you and your doctor may need to discuss whether or not to continue with the pregnancy. Providing treatment right away may be the safest option if you have an advanced or aggressive cancer that is found early in the pregnancy.


Generally, surgery may be considered the safest cancer treatment option for some cancers, especially after the first trimester. Improvements in surgery and careful monitoring make it possible to lessen the risks to both you and your baby.

Chemotherapy and other drug therapies

Chemotherapy is the use of anticancer drugs to treat cancer. It is a systemic therapy. This means that the drug travels throughout the blood to find and destroy cancer cells. Chemotherapy and other drugs used to treat cancer are toxic and some have the potential to harm a baby, especially if they are given during the first trimester of pregnancy, when the organs of the baby are developing.

Doctors sometimes try to delay giving chemotherapy to minimize the effects on the baby. The decision to delay chemotherapy depends on how advanced the cancer is and how quickly it has developed.

Chemotherapy during the first trimester can cause birth defects and low birth weights or may cause a miscarriage. The risk of birth defects when chemotherapy is given during the first trimester varies according to the type of chemotherapy used.

Although some chemotherapy drugs given during the second and third trimesters are associated with low birth weight and stillbirth (delivery of a baby who has died), many chemotherapy and other drugs may be given during the second and third trimesters without causing harm to the baby. A lot of protection is provided by the placenta. The placenta develops during pregnancy and connects the blood supplies of the mother and baby. It provides nutrients and removes waste products. It also acts as a barrier between the mother and the baby that many chemotherapy drugs cannot pass through.

Chemotherapy is usually not recommended after 35 weeks of pregnancy (3 weeks before childbirth) because it can lower your blood cell counts, which can cause bleeding and increased risk of infection during childbirth. Stopping chemotherapy during this time can allow you to recover bone marrow that you may have lost during treatment. It may also give the placenta time to help remove drugs from the baby's body and allow time for your own blood counts to return to normal before childbirth.

Some effects of chemotherapy and other drug therapies on a baby are not known, especially for newer drugs like biological therapies or targeted therapies. Chemotherapy and other drug therapies can cause health problems in the woman such as infection, anemia or nausea and vomiting. These problems can indirectly harm a baby.

Radiation therapy

Radiation therapy uses high-energy x-rays or particles to destroy cancer cells and shrink tumours. Radiation is usually not done during pregnancy because it can harm a baby, especially during the first trimester when the baby's organs and nervous system are developing. Whether or not radiation therapy can be used in the second or third trimester depends on the dose of radiation and the area of the body being treated. The International Commission on Radiological Protection has developed guidelines for safe radiation exposure during pregnancy.

When radiation therapy is possible, careful planning is used to treat you if you have a cancer that is far away from the growing baby in the pelvis (such as head and neck cancers). Lead shields or blocks are used to reduce as much as possible the amount of radiation the baby is exposed to. Radiation therapy for breast cancer can usually be delayed until after the baby is born.

Cancers in the pelvis cannot be treated effectively with radiation therapy without causing severe problems for the baby regardless of the stage of pregnancy. Possible effects on the baby during this time include miscarriage, birth defects, abnormal brain function and slow growth. If the pregnancy is between 1 and 26 weeks, the doctor will often recommend not to continue with the pregnancy. If the cancer is found later in the pregnancy, treatment can often be delayed until after delivery.


Cancer cells cannot pass to the infant through breast milk. But chemotherapy and other drugs can be transferred to the baby, and this can cause harm. Radioactive substances that are taken as a drink or a pill (such as radioactive iodine used to treat thyroid cancer) can also get into the breast milk and harm the baby. So you may be told to stop breastfeeding for a period of time or not to breastfeed at all if you need systemic therapy, like chemotherapy.

Always ask the healthcare team if it is safe for you to breastfeed.


Your prognosis (estimated outcome) when you are pregnant and have cancer is often the same as the prognosis for women who are not pregnant but who are the same age with the same type and stage of cancer.

Expert review and references

  • Ellen Warner, MD, MSc, FRCPC
  • Nadine Shehata, MD, MSc, FRCPC
  • Alon Altman, H.BSc., MD, FRCSC
  • Dawn Maze, MD, FRCPC, MSc

Medical disclaimer

The information that the Canadian Cancer Society provides does not replace your relationship with your doctor. The information is for your general use, so be sure to talk to a qualified healthcare professional before making medical decisions or if you have questions about your health.

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