Pregnancy and Breast Cancer

Very few pregnant women are diagnosed with breast cancer. But more women are choosing to have children later in life. Because the risk of breast cancer increases as women get older, doctors expect there will be more cases of breast cancer during pregnancy in the future.

Estimates are that about 1 out of 1,000 pregnant women is diagnosed with cancer, with about 3,500 cases diagnosed each year. The most common type of cancer found during pregnancy or in the first year after pregnancy is breast cancer. You may hear this called gestational breast cancer or pregnancy-associated breast cancer.

Breast cancer risk

What is cancer?

Normal body cells grow, divide, and die in an orderly fashion. During the early years of a person’s life, normal cells divide more quickly until the person becomes an adult. After that, cells in most parts of the body divide only to replace worn-out or dying cells and to repair injuries.

Cancer cells keep on growing and dividing, which makes them very different from normal cells. Instead of dying, they outlive normal cells and keep making new, abnormal cells. Hormones like estrogen help normal breast cells grow and divide, but hormones can also promote the growth of breast cancer cells.

How your menstrual cycles affect breast cancer risk

Women who are exposed to higher levels of estrogen over longer periods of time seem to have a slightly higher risk for breast cancer. This includes women who had more menstrual periods, such as those who started menstruating before age 12 or who went through menopause after age 55.

How pregnancy affects breast cancer risk later in life

Pregnancy causes many hormone changes in the body. For one thing, pregnancy stops the monthly menstrual cycles and shifts the hormone balance toward progesterone rather than estrogen. This is why women who become pregnant while they are young and have many pregnancies may have a slightly lower risk of breast cancer later on. Women who have had no children or who had their first pregnancy after age 30 have a slightly higher breast cancer risk later in life.

How breast-feeding affects breast cancer risk

Some studies have suggested that breast-feeding may slightly lower breast cancer risk. This is more likely if breast-feeding goes on for 1½ to 2 years or if many children are breast-fed. The reason for this may be that both pregnancy and breast-feeding reduce a woman’s total number of lifetime menstrual cycles. More research is needed to look into the effects of breast-feeding.

Finding breast cancer during pregnancy

When a pregnant woman develops breast cancer, it is often diagnosed at a later stage than it is in women who are not pregnant. It is also more likely to have spread to the lymph nodes. This is partly because during pregnancy hormone changes cause a woman’s breasts to get larger, tender, and lumpy. This can make it harder for you or your doctor to notice a lump in your breasts until it gets quite large. Mammograms are also harder for doctors to read during pregnancy because the breast tissue becomes denser. The early changes caused by cancer are easily mistaken for or hidden by the normal changes that happen with pregnancy.

Mammograms can detect most of the cancers that start during pregnancy. But screening may be postponed because some patients (and even doctors) worry about the safety of doing a mammogram during pregnancy. But it is fairly safe to have a mammogram during pregnancy. The amount of radiation needed for a mammogram is small. And the radiation is focused on the breast so that most of it does not reach other parts of the body. For extra protection, a lead shield is placed over the lower part of the belly to stop radiation from reaching the womb. Still, scientists can’t be certain about the effects of even a small dose of radiation on an unborn baby. If your doctor does not believe you need to have your mammogram right away, it may be best to wait. Other imaging tests that do not use radiation, such as breast ultrasound, may be used instead. These are thought to be safe alternatives to mammograms during pregnancy.

Even during pregnancy, early detection is an important part of breast health. Talk to your doctor or nurse about breast exams and the best time for your next mammogram, especially if you are age 40 or older, or if you or your doctor notices a change in how your breasts look or feel. As always, if you find any lump or change in your breasts, tell your doctor or nurse right away.

Breast cancer diagnosis and staging during pregnancy

Biopsy

A new lump or abnormal imaging test result may cause concern, but a biopsy is needed to find out if it is breast cancer. During a biopsy a piece of tissue is taken from the area of concern. This is usually done either using a long, hollow needle or through a small surgical incision (cut). A breast biopsy during pregnancy can usually be done as an outpatient procedure. The doctor uses medicine to numb just the area of the breast involved in the biopsy. This causes little risk to the fetus. But a biopsy can be done under general anesthesia (where drugs are used to put the patient into a deep sleep) if needed, with only a small risk to the fetus.

You can get more details on different types of breast biopsies in our document called For Women Facing a Breast Biopsy.

Tests to learn the cancer stage

If breast cancer is found, other tests may be needed to find out if cancer cells have spread within the breast or to other parts of the body. This process is called staging. Staging tests are very important for pregnant women with breast cancer because their cancers tend to be found at a more advanced stage (the tumor is likely to be bigger and to have spread beyond the breast). Which staging tests may be needed depends on your case.

Keep in mind that the fetus is not exposed to radiation with tests like ultrasound and magnetic resonance imaging (MRI) scans. Overall, these tests are thought to be safe and can be used if they are important to your care. But the contrast material (dye) sometimes used in MRI crosses the placenta, the organ that connects the mother to the fetus. It has been linked with fetal abnormalities in lab animals. For this reason, an MRI that uses contrast dye is not recommended during pregnancy. But an MRI without contrast can be used if needed.

Chest x-rays are sometimes needed to help make treatment decisions. They use a small amount of radiation. They are thought to be safe for pregnant women when the belly is shielded.

Other tests, such as bone scans or computed tomography (CT) scans of the chest, abdomen (belly), or pelvis, are more likely to expose the fetus to radiation. These tests are not often needed, especially if the cancer is thought to be just in the breast. In rare cases when these scans are needed, doctors can adjust the way the test is done to limit the amount of radiation the fetus is exposed to.

In very few cases, the cancer has reached the placenta (the organ that connects the mother to the fetus). This could affect the amount of nutrition the fetus gets from the mother, but there are no reported cases of breast cancer being transferred from the mother to the fetus.

Breast cancer treatment during pregnancy

If breast cancer is found during pregnancy, the type and timing of treatment depends on many things, such as:

• The size of the tumor
• Where the tumor is
• Whether and how far the cancer has spread
• How far along the pregnancy is
• What the woman prefers

Treating a pregnant woman with breast cancer has the same goals as treating a non-pregnant woman: control the cancer in the place where it started and keep it from spreading. But protecting a growing baby may make reaching these goals more complex.

If a pregnant woman needs chemotherapy, hormone therapy, or radiation to treat breast cancer, she may be asked to think about ending the pregnancy. This is because these treatments may harm the fetus. It is easier to treat a woman who is not pregnant because there is no fear of harming the fetus. But no studies have proven that ending a pregnancy in order to have cancer treatment improves the woman’s prognosis (outlook for survival). Still, this is an option that may be discussed when looking at all the treatment choices available.

Surgery

When possible, surgery is the first treatment for any woman with breast cancer, including those who are pregnant. Removing the tumor (lumpectomy) or the entire breast (mastectomy), and/or taking out the lymph nodes under the arm carry little risk to the fetus. But there are certain times in pregnancy when anesthesia (the drugs used to make you sleep for surgery) may be riskier for the fetus. Many doctors, such as a high-risk obstetrician, a surgeon, and an anesthesiologist will need to work together to decide the best time during pregnancy to do surgery. If the surgery is done later in the pregnancy, the obstetrician may be there just in case there are any problems with the baby during surgery. Together, these doctors will decide which drugs and techniques are the safest for both the mother and the baby.

Mastectomy can often be used as the first treatment for early stage cancers. Lymph nodes in the armpit may also need to be taken out if there is suspicion that the cancer has spread there. Depending on the how far along you are in pregnancy and your cancer stage, your doctor may not be able to do a sentinel lymph node biopsy (SNLB). This is when tracers and dye are used to pinpoint the nodes most likely to contain cancer cells. SNLB allows the doctor to remove of fewer nodes. But there is concern that the radioactive tracer used for SNLB may affect the fetus if used during times organs are growing quickly. More research is needed on this.

Depending on the cancer’s stage, a woman may get more treatment such as chemotherapy, radiation, and/or hormone therapy after surgery to help lower the risk of the cancer coming back. This is called adjuvant treatment.

Women who have breast-saving surgery, like lumpectomy, often need radiation therapy afterward to reduce the chance that the cancer will come back. The need for radiation is an important issue for pregnant women when choosing which surgery to have. Radiation could affect the fetus if given during the pregnancy, so it is not used until after the birth. Doctors don’t know how this delay may affect a woman’s risk of the cancer coming back. Cancer found in the third trimester may involve very little delay in radiation treatments, so there would likely be no effect on outcome. And a woman who will be getting chemotherapy before radiation may have little or no delay in her radiation treatments. But cancers found early in the pregnancy may mean a longer delay in starting radiation. Treatment must always be considered on a case-by-case basis.

Chemotherapy

Chemotherapy, which is also called “chemo,” may be used along with surgery (as an adjuvant treatment) for some earlier stages of breast cancer. It also may be used by itself for more advanced cancers.

Chemo usually is not given during the first 3 months of pregnancy (the first trimester). This is because most of the fetus’s internal organs develop during this time. The risk of miscarriage (losing the baby) is also the greatest during the first trimester. The safety of chemo during this time has not been studied because of concerns about damage to the fetus.

It was once thought that all chemo drugs would harm the fetus. But studies have shown that certain chemo drugs used during the second and third trimesters (the fourth through ninth months of pregnancy) do not raise the risk of birth defects, stillbirths, or health problems shortly after birth. But researchers still do not know whether these children will have any long-term effects.

When a pregnant woman with early breast cancer needs adjuvant chemo after surgery, it’s usually delayed until at least the second trimester. If a woman is already in her third trimester when the cancer is found, the chemo may be delayed until after birth. The birth may be induced (brought on) a few weeks early in these cases. Depending on the extent of the cancer, these same treatment plans may also be used for women whose disease is more advanced.

Chemo should not be given 3 to 4 weeks before delivery. This is because one side effect of chemo is that it lowers the mother’s blood counts. This could cause bleeding and increase the chances of infection during birth. Holding off on chemo for the last few weeks before delivery allows the mother’s blood counts to return to normal levels before childbirth.

Radiation therapy

Radiation therapy to the breast is often used after breast-conserving surgeries (lumpectomy or partial mastectomy) to reduce the risk of the cancer coming back. The high doses of radiation used for this can harm the fetus any time during pregnancy. It may cause miscarriage, birth defects, slow fetal growth, or a higher risk of childhood cancer so doctors do not recommend its use during pregnancy.

Pregnant women who choose lumpectomy or partial mastectomy can usually have surgery during the pregnancy and wait until after the baby is born to have radiation therapy. But this treatment approach has not been well-studied in pregnant women. And it is not known if the time delay might affect how well the radiation works.

Hormone therapy

Hormone therapy, such as treatment with tamoxifen, may be used as adjuvant treatment after surgery or as treatment for advanced cancer. Its use in pregnant women has not been well-studied, so its effects are not known. But there have been reports of miscarriage and fetal death, as well as head and face birth defects and genital defects in babies born to women who became pregnant while taking tamoxifen in early pregnancy.

More study in this area is needed. But at this time it is recommended that hormone therapy for breast cancer be delayed until after the woman has given birth.

Breast-feeding during cancer treatment

Most doctors recommend that women who have just had babies and are about to be treated for breast cancer should stop (or not start) breast-feeding.

If surgery is planned, stopping breast-feeding will help reduce blood flow to the breasts and make them smaller. This can help with the operation. It also helps reduce the risk of infection in the breast and can help avoid having breast milk collect in biopsy or surgery areas.

Many chemo and hormone therapy drugs can enter breast milk and could be passed on to the baby. So, if the mother is getting chemo or hormone therapy, she shouldn’t breast-feed.

If you have specific questions, such as when it might be safe to start breast-feeding, be sure to talk with your health care team. If you plan to start back after you’ve stopped breast-feeding for a while, you will want to plan ahead. You may need extra help from breast-feeding experts.

Pulling all the treatment plans together

The hardest part of treatment is when there is a conflict between the best known treatment for the mother and the well-being of the fetus. A woman who is found to have breast cancer during a pregnancy may have hard choices to make – she needs to know all her options and she needs expert help. Her obstetrician will need to work with her surgeon, her oncologist, her radiation oncologist, and others involved in her care. Through all this, the woman with breast cancer will need emotional support, so a counselor or psychologist should also be part of her care team.

It is important to know that when compared by cancer stage, outcomes of breast cancer in pregnant women are much the same as the outcomes in women who are not pregnant. If you would like more information on breast cancer and its treatment, please read our document called Breast Cancer.

Effect of pregnancy on survival after breast cancer

Pregnancy during breast cancer

Pregnancy may make it harder to find, diagnose, and treat breast cancer. But most studies have found that the outcomes among pregnant and non-pregnant women with breast cancer are about the same for cancers found at the same stage.

Some doctors believe that ending the pregnancy may help slow the course of more advanced breast cancers, and they may recommend an abortion in these cases. Ending the pregnancy may make treatment simpler, but it has not been shown that it improves the women’s outcomes. It is hard to do research in this area, and very few good studies exist. Still, the studies that have been done have not found that ending the pregnancy improves a woman’s overall survival or cancer outcome, and there are no reports showing that breast cancer is harmful to the baby.

Studies have not shown that the treatment delays sometimes needed during pregnancy have an effect on breast cancer outcome either. But this, too, has proven to be a difficult area to study.

Pregnancy after breast cancer treatment

Some treatments for breast cancer, such as certain chemo drugs, may affect a woman’s ability to have a baby (fertility). Still, many women are able to become pregnant after treatment. Women concerned about their fertility should talk to their doctors about this before starting breast cancer treatment.

Doctors are not sure if women who have had breast cancer in the past increase their risk of the cancer coming back by becoming pregnant. But most studies done on this have found that pregnancy does not increase the risk of the cancer coming back after successful treatment.

Doctors do know that there is a clear link between estrogen levels and growth of breast cancer cells. Because of this link, many doctors advise breast cancer survivors to wait at least 2 years after treatment before trying to get pregnant, though the best length of time to wait is not clear. Two years is thought to give them the chance to find any early return of the cancer, which could affect a woman’s decision to become pregnant later on. Still, this advice is not based on data from any clinical trials. And some studies point out that breast cancer can come back after the 2 year mark, so every case is different. Each woman’s decision is based on many things, such as her age, fertility, desire for more pregnancies, type of breast cancer, risk of an early relapse, and the potential effect estrogen may have on her risk of a breast cancer coming back.

Women taking hormone therapy, such as tamoxifen, should talk with their doctors before trying to become pregnant. These drugs could affect a growing fetus (see the section, “Hormone therapy”).

There is no proof that a woman’s past breast cancer has any direct effect on her baby. Researchers have found no increased rate of birth defects or other long-term health concerns in children born to women who have had breast cancer.

There is also no proof that breast feeding after breast cancer treatment shortens survival. But women who have had breast surgery and/or radiation should know that they may have problems breast feeding from the affected breast. Studies have shown reduced milk production in that breast as well as structural changes can make latching difficult and painful.

Another important thing to remember is that chemotherapy for breast cancer can damage the ovaries, sometimes causing immediate or delayed infertility. Cancer treatment can also cause women to delay trying to get pregnant. These factors together often mean that a woman has less of a chance of getting pregnant after breast cancer treatment. For more information about how cancer treatment can affect fertility, see our document called Fertility and Cancer: What Are my Options?

All women who have had breast cancer and are thinking about having children should talk with their doctors about how the treatment they got can affect their chances for pregnancy. They will also want to know their risk of cancer coming back. In many cases, counseling can help women sort through the choices that come with surviving breast cancer and planning a pregnancy.

Additional resources

More information from your American Cancer Society

We have listed some related information that may also be helpful to you. Free copies of these may be ordered from our toll-free number, 1-800-227-2345, or they can be read on our Web site at www.cancer.org.

Breast Cancer (also available in Spanish)

For Women Facing a Breast Biopsy (also available in Spanish)

Choosing a Doctor and a Hospital (also available in Spanish)

Fertility and Cancer: What Are My Options?

Understanding Chemotherapy: A Guide for Patients and Families (also available in Spanish)

Understanding Radiation Therapy: A Guide for Patients and Families (also available in Spanish)

After Diagnosis: A Guide for Patients and Families (also available in Spanish)

Talking With Your Doctor (also available in Spanish)

National organizations and Web sites*

Along with the American Cancer Society, other sources of information and support include:

Y-Me National Breast Cancer Organization
Toll-free number: 1-800-221-2141
Web site: www.y-me.org

Patients and survivors may be matched with someone who has had the same diagnosis and is the same age. Partners of breast cancer patients may also get support from others; community-based support groups are also offered

National Cancer Institute
Toll-free number: 1-800-422-6237
TYY: 1-800-332-8615
Web site: www.cancer.gov

Information about cancer and its treatment, living with cancer, and more. Find special information for pregnant women with breast cancer at: www.cancer.gov/cancertopics/pdq/treatment/breast-cancer-and-pregnancy/Patient

Hope for Two: The Pregnant With Cancer Network
Toll-free number: 1-800-743-4471
Web site: www.hopefortwo.org

Has phone and online support, an info packet, and a newsletter for pregnant women with cancer. Also offers women who have been through it the chance to volunteer to help others

Young Survival Coalition
Toll-free number: 1-877-972-1011
Web site: www.youngsurvival.org

Offers resources, support, and information to women diagnosed with breast cancer at ages 40 and under (some Spanish materials also available)

US Food and Drug Administration Pregnancy Exposure Registries Information
Toll-free number (for certain cancer drugs only): 1-877-635-4499
Web site: www.fda.gov/ScienceResearch/SpecialTopics/WomensHealthResearch/ucm134848.htm

Allows women who have had certain cancer treatments while pregnant to share the chemotherapy effects on their babies with other women who need cancer treatment

No matter who you are, we can help. Contact us anytime, day or night, for cancer-related information and support. Call us at 1-800-227-2345 or visit www.cancer.org.

References

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