Cancer During Pregnancy

Cancer during pregnancy is rare, occurring in approximately one out of every 1,000 pregnancies, and little research is available to guide women and doctors. However, a pregnant woman with cancer is capable of giving birth to a healthy baby, and some cancer treatments are safe during pregnancy. Cancer rarely affects the fetus directly. Although some cancers may spread to the placenta (a temporary organ that connects the mother and fetus), most cancers cannot spread to the fetus itself.

The cancers that tend to occur during pregnancy are those that are more common in younger people, such as cervical cancer, breast cancer, thyroid cancer, Hodgkin lymphoma, and melanoma. In addition, a gestational trophoblastic tumor is a rare cancer that occurs in a woman's reproductive system. It is most commonly the result of an abnormal combination of a sperm and an egg; in other cases, it begins from a normal placenta.

Because age is the most significant risk factor for cancer, the rate of cancer during pregnancy may be increasing as more women are waiting until they are older to have children.

Diagnosis

Being pregnant often delays a cancer diagnosis because some cancer symptoms such as abdominal bloating, frequent headaches, or rectal bleeding are common during pregnancy and are not considered suspicious.

Breast cancer is the most common cancer in pregnant women, affecting approximately one in 3,000 pregnancies. Pregnancy-related breast enlargement may make it difficult to detect small breast tumors, and mammograms are not regularly done during pregnancy.

If cancer is suspected during pregnancy, women and their doctors may be concerned about diagnostic tests such as x-rays. However, research has shown that the level of radiation in diagnostic x-rays is too low to harm the fetus. When possible, women may use a lead shield that covers the abdomen for extra protection. Other diagnostic tests—such as magnetic resonance imaging (MRI), ultrasound, andbiopsy—are also considered safe during pregnancy because they don't use ionizing radiation.

Sometimes, pregnancy can uncover cancer that had previously gone undetected. For example, a Pap test performed as part of standard prenatal care can detect cervical cancer. Similarly, an ultrasound performed during pregnancy can find ovarian cancer that might otherwise go undiagnosed.

Treatment

When making treatment decisions for cancer during pregnancy, the doctor considers the best treatment options for the mother and the possible risks to the fetus. The type of treatment given depends on many factors, including gestational age of the fetus (stage of the pregnancy); the type, location, size, and stage of the cancer; and the wishes of the expectant mother and family. Because some cancer treatments can harm the fetus, especially during the first trimester (the first three months of pregnancy), treatment may be delayed until the second or third trimesters. When cancer is diagnosed later in pregnancy, doctors may wait to start treatment until after the baby is born, or they may consider inducing labor early. In some cases, such as early-stage (stage 0 or IA) cervical cancer, doctors may wait to treat the cancer until after delivery.

Some cancer treatments may be used during pregnancy but only after careful consideration and treatment planning to optimize the safety of the mother and the unborn baby. These include surgery, chemotherapy, and rarely, radiation therapy.

Surgery. Surgery is the removal of the tumor and surrounding tissue during an operation. It poses little risk to the fetus and is considered the safest cancer treatment option during pregnancy. In some instances, more extensive surgery can be done to avoid having to use chemotherapy or radiation therapy.

Chemotherapy. Chemotherapy is the use of drugs to kill cancer cells, usually by stopping the cancer cells' ability to grow and divide. Chemotherapy can harm the fetus, particularly if it is given during the first trimester of pregnancy when the fetus' organs are still developing. Chemotherapy during the first trimester may cause birth defects or even the loss of the unborn baby. During the second and third trimesters, some types of chemotherapy may be given without necessarily harming the fetus. The placenta acts as a barrier between the mother and the fetus, and some drugs cannot pass through the barrier, or they pass through only minimally. If the planned chemotherapy includes a drug that is not safe during any stage of pregnancy, the doctor can sometimes substitute another drug. Although chemotherapy in the later stages of pregnancy may not directly harm the fetus, it may cause side effects—such as malnutrition and anemia, meaning a low read blood cell count—for the mother that may indirectly harm the fetus. In addition, chemotherapy given during the second and third trimesters often causes early labor and low birth weight, both of which may lead to further health concerns for the mother and the baby. The baby may struggle to gain weight and fight infections, and the mother may have trouble breastfeeding.?

Radiation therapy. Radiation therapy is the use of high-energy x-rays or other particles to kill cancer cells. Because radiation therapy can harm the fetus, particularly during the first trimester, doctors generally avoid using this treatment. Even in the second and third trimesters, the use of radiation therapy is rare, and it depends on the dose of radiation and the area of the body being treated. 

Breastfeeding

Although cancer cells cannot pass to the infant through breast milk, doctors advise women who are being treated for cancer not to breastfeed. Chemotherapy can be especially dangerous because the drugs may be transferred to the infant through the breast milk, causing harm. Similarly, radioactive components that are taken internally, such as radioactive iodine used in treating thyroid cancer, also cross into breast milk and can harm the infant.

How pregnancy affects chance of recovery from cancer

The prognosis (chance of recovery) for a pregnant woman with cancer is often the same, compared with other women of the same age with the same type and stage of cancer. However, if a woman's diagnosis is delayed during pregnancy, the extent of the cancer at the time of diagnosis may be greater, resulting in a worse overall prognosis. In addition, pregnancy sometimes affects the behavior of some cancers. For example, there is some evidence to suggest that the hormonal changes of pregnancy may stimulate the growth of malignant melanoma.

Pregnancy after cancer treatment

As more young people are surviving cancer, more women are considering whether they should have a baby after having cancer. In general, pregnancy after cancer treatment is considered safe for both the mother and the baby, and pregnancy does not appear to increase the chances of cancer recurring (coming back). However, because some cancers do recur, women are usually advised to wait a number of years after completing cancer treatment until the risk of recurrence has decreased. The amount of time a patient may be advised to wait before trying to become pregnant depends on the type and stage of cancer, the type of treatment the patient received, and the patient's preferences.

Sometimes, cancer treatments can damage specific areas of the body, such as the heart or lungs. Before becoming pregnant, your doctor may need to evaluate these organs to be sure that the pregnancy will be safe.

Unfortunately, some cancer treatments also cause infertility, making it difficult or impossible for some women to have children. All women of childbearing age who are interested in having children in the future should talk with their doctor about treatment-related infertility risks and fertility preservation strategies before beginning treatment. 

Read ASCO's guideline on fertility preservation and cancer treatment to learn about options to preserve fertility before cancer treatment.