Pregnancy and Cancer

Cancer during pregnancy is fortunately rare. Little research is available to guide patients and doctors. It is known that in some cases a pregnant woman with cancer is capable of giving birth to a healthy baby and that certain cancer treatments are safe during pregnancy.

Prevalence

Cancer occurs in approximately one out of every 1,000 pregnancies. However, pregnancy itself does not cause cancer, and pregnant women are not more susceptible to cancer than other women. The cancers that tend to occur during pregnancy are those that are more common in younger people, such as cervical cancer, breast cancer, Hodgkin lymphoma, malignant melanoma, and thyroid cancer. Because age is the most significant risk factor for cancer, doctors expect the rate of cancer during pregnancy to increase as more women are waiting until they are older to have children.

Diagnosis

Being pregnant can delay a cancer diagnosis. Symptoms such as abdominal bloating, frequent headaches, or rectal bleeding might suggest ovarian, brain, or colon cancer. These symptoms are also common during pregnancy and are not considered suspicious. In rare cases in which these symptoms are related to cancer, diagnosis of the cancer is likely to be delayed.

Breast cancer is the most common cancer in pregnant women, affecting approximately one in 3,000 pregnancies. Pregnancy-related breast enlargement makes it difficult to detect small breast tumors, and mammograms are not routinely 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, a lead shield covering the abdomen offers extra protection. Other diagnostic tests, such as magnetic resonance imaging tests (MRIs), ultrasounds, and biopsies, are also considered safe during pregnancy because they don't use radiation.

Sometimes, pregnancy can uncover cancer that had previously gone undetected. A Pap test performed as part of routine, early prenatal care can detect cervical cancer. Similarly, routine ultrasounds performed during pregnancy can often detect ovarian cancer that might otherwise go undiagnosed.

Treatment

Treatment for cancer during pregnancy means balancing optimal treatment for the mother against possible risk to the fetus. The type of treatment given will depend on many factors, including how far the pregnancy has progressed; 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.

Cancer treatments used during pregnancy may include surgery, chemotherapy, and in some cases, radiation therapy, but only after careful consideration and treatment planning to ensure maternal and fetal safety.

Surgery 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 is the use of drugs to kill cancer cells. Chemotherapy is toxic and capable of harming the fetus, particularly if given during the first trimester of pregnancy when the fetus' organs are still developing. Chemotherapy during the first trimester can cause birth defects or miscarriage (early pregnancy loss). During the second and third trimesters, chemotherapy can be taken without harming the fetus. The placenta (the organ that develops during pregnancy) acts as a barrier between the mother and the fetus that most chemotherapy cannot pass through. When the standard chemotherapy regimen includes a drug that is not safe during any stage of pregnancy, another drug can usually be substituted.

Although chemotherapy later in pregnancy may not directly harm the fetus, chemotherapy can cause health problems for the mother that can indirectly harm the fetus, such as malnutrition and anemia (low red blood cell count). Chemotherapy given during the second and third trimesters can cause early labor and low birth weight, both of which may lead to further complications, such as problems with breast-feeding, gaining weight, and fighting infections.
Radiation therapy involves high energy x-rays to destroy cancer cells and shrink cancerous tumors. Because radiation therapy can harm the fetus, particularly during the first trimester, this treatment is generally not recommended. The use of radiation therapy in the second or third trimesters depends on the dose of radiation and the area of the body being treated.

Prognosis and fetal outcome

In most cases, the prognosis (chance of recovery) for a pregnant woman with cancer is the same as for another woman of the same age with the same type and stage of cancer. However, if diagnosis is delayed during pregnancy, women tend to have a worse, overall prognosis than non-pregnant women diagnosed with cancer. In addition, pregnancy can affect 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.

Cancer rarely affects the fetus directly. Although some cancers can metastasize to the placenta, most cancers cannot metastasize to the fetus itself. In rare cases, malignant melanoma is capable of spreading to the placenta and the fetus.

Breast-feeding

Although cancer cells cannot pass to the infant through breast milk, women who are being treated for cancer are generally advised not to breast-feed. Chemotherapy can be especially dangerous as it can build up in breast milk and harm the infant. 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.

Pregnancy after cancer

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 is considered safe for both the mother and the baby, and pregnancy does not appear to increase the chances of cancer recurring. However, since 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 you will be advised to wait before becoming pregnant depends on the type and stage of cancer and course of treatment.

In some cases, cancer treatments can cause damage to areas of the body such as the heart or lungs. Before becoming pregnant, these organs may need to be evaluated to be sure that the pregnancy will be safe.

Unfortunately, some cancer treatments can also cause infertility, making it difficult or impossible for some women to have children. For more information on cancer and infertility, including information on how to preserve fertility before cancer treatment, read the previous section, Fertility and Cancer Treatment.

More Information

Parenting While Dealing with Cancer

Cancer in Young Adults

Additional resources

Pregnant with Cancer Network

National Cancer Institute: Breast Cancer and Pregnancy

National Cancer Institute: Hodgkin's Lymphoma During Pregnancy

National Cancer Institute: Non-Hodgkin's Lymphoma During Pregnancy

American Cancer Society: Pregnancy and Breast Cancer