Breast cancer is found in about 1 in every 3,000 pregnant women. And breast cancer is the most common type of cancer found during pregnancy, while breastfeeding, or within the first year of delivery. You may hear this called gestational breast cancer or pregnancy-associated breast cancer (PABC). The special concerns of breast cancer during pregnancy are reviewed here.
Breast cancer risk
What is cancer?
The body is made up of trillions of living cells. Normal body cells grow, divide into new cells, and die in an orderly way. In babies and children, 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 starts when cells in a part of the body start to grow out of control. Instead of dying, they outlive normal cells and keep making new, abnormal cells. Cancer cells keep growing out of control, and invade (grow into) other tissues – something normal cells can’t do.
Hormones like estrogen help normal breast cells grow and divide, but these same hormones can also promote the growth of breast cancer cells.
How your menstrual cycles affect your breast cancer risk
Women who have had more menstrual cycles because they started their periods earlier (before age 12) and/or went through menopause later (after age 55) have a slightly higher risk of breast cancer. The increase in risk may be due to a longer lifetime exposure to the hormones estrogen and progesterone.
How pregnancy affects breast cancer risk later in life
Pregnancy causes many hormone changes in the body. For one thing, pregnancy stops 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. They are exposed to less estrogen. Women who have had no children or who had their first pregnancy after age 30, on the other hand, have a slightly higher breast cancer risk.
How breastfeeding affects breast cancer risk
Some studies suggest that breastfeeding may slightly lower breast cancer risk. This is more likely if a woman breastfeeds for 1½ to 2 years. But this has been a difficult area to study, especially in countries like the United States, where breastfeeding for this long is uncommon.
One way to explain this possible effect may be that breastfeeding reduces a woman’s total number of lifetime menstrual cycles. This is much like starting menstrual periods at a later age or going through early menopause.
Finding breast cancer during pregnancy
When a pregnant woman develops breast cancer, it’s often diagnosed at a later stage than it would be if the woman were not pregnant. It’s also more likely to have spread to the lymph nodes. This is partly because hormone changes during pregnancy make a woman’s breasts larger, more tender, and lumpy. This can make it harder for the woman or her doctor to notice a lump until it gets quite large.
Another reason it may be hard to find breast cancers early during pregnancy is that pregnancy makes breast tissue denser. Dense breast tissue can hide an early cancer on a mammogram. Also, the early changes caused by cancer can be easily mistaken for the normal changes that happen with pregnancy. Delayed diagnosis remains one of the biggest problems with breast cancer in pregnancy.
If you find a lump or notice any changes in your breasts, take it seriously. If your doctor doesn’t want to check it out with tests such as a mammogram, ask about other kinds of imaging tests or get a second opinion. Any suspicious breast changes should be biopsied before assuming they are a normal response to pregnancy.
Mammograms can find most breast cancers that start when a woman is pregnant, and it’s thought to be 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 breasts, 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 very small dose of radiation on an unborn baby.
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. As always, if you find a lump or change in your breasts, tell your doctor or nurse right away.
Breast cancer diagnosis and staging during pregnancy
Breast biopsy during pregnancy
A new lump or abnormal imaging test result may cause concern, but a biopsy is needed to find out if a breast change is 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 needle biopsy (even on a pregnant woman) is usually 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, if needed, a surgical biopsy can be done under general anesthesia (where drugs are used to put the patient into a deep sleep) 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 stage of the breast cancer
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 is 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 with contrast dye is not recommended during pregnancy. But an MRI can be used without contrast 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 PET scans, bone scans, and computed tomography (CT) scans 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 treatment recommendations depend on things such as:
The size of the tumor
Where the tumor is
If the cancer has spread and if it has, how far
How far along the pregnancy is
What the woman prefers
Treating a pregnant woman with breast cancer has the same goal as treating a non-pregnant woman: control the cancer in the place where it started and keep it from spreading. But the extra concern of protecting a growing baby may make reaching these goals more complex.
If a pregnant woman needs chemotherapy, hormone therapy, or radiation right away to treat breast cancer in early pregnancy, she may be asked to think about ending the pregnancy. This is because these treatments may harm the fetus. It’s easier to treat a woman who is not pregnant because there is no fear of harming the fetus.
For some breast cancers, such as inflammatory breast cancer, a delay in treatment would likely harm the patient. Older studies reportedly found that ending a pregnancy in order to have cancer treatment didn’t improve a woman’s prognosis (outlook). (See the section “Survival rates after breast cancer during pregnancy” for further discussion on this.) Even though there were flaws in these studies, ending the pregnancy is no longer routinely recommended when breast cancer is found. Still, this option may be discussed when looking at all the treatment choices available, especially in aggressive cancers that may need immediate treatment. Women and their families need to fully understand the risks and benefits of all their options before making treatment decisions.
Surgery
When possible, surgery is a major part of treatment for any woman with early breast cancer. For women who are pregnant is it likely to be the first treatment as well. Removing only the part of the breast with the tumor (breast-conserving surgery) 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.
For many cancers, either mastectomy or breast-conserving surgery (BCS) can be used to remove the cancer in the breast. Mastectomy is used more often for pregnant women with breast cancer because women who have breast-conserving surgery need radiation therapy afterward.
The need for radiation is an important issue for pregnant women when choosing which surgery to have. Radiation could affect the fetus if it is given during the pregnancy, so it can’t be given until after delivery, and delaying radiation too long could increase the chance of the cancer coming back. Cancer that’s found in the third trimester may mean very little delay in radiation treatments, so there would probably be no effect on outcome. And radiation is normally given after chemotherapy (chemo), so a woman who will be getting chemo after surgery 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.
One or more lymph nodes in the armpit also need to be removed to check for cancer spread. One way to do this is an axillary lymph node dissection. This removes many of the lymph nodes under the arm. Another procedure that may be an option depending on the how far along you are in pregnancy and your cancer stage, is a sentinel lymph node biopsy (SNLB). This procedure uses tracers and dye to pinpoint the nodes most likely to contain cancer cells. SNLB allows the doctor to remove fewer nodes. But there are concerns about the effects the radioactive tracer and blue dyes that are used for SNLB might have on the fetus. Because of these concerns, some experts recommend that SLNB only be used later in pregnancy. More research is needed on these concerns.
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. In some cases, this treatment can be put off until after delivery.
More information about the kinds of surgery used to treat breast cancer can be found in our document, Breast Cancer.
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 is not given during the first 3 months of pregnancy (the first trimester). Because most of the baby’s internal organs develop during this time, the safety of chemo hasn’t been studied in the first trimester. The risk of miscarriage (losing the baby) is also the greatest during this time.
For many years, it was thought that all chemo would harm an unborn baby no matter when it was given. But studies have shown that certain chemo drugs used during the second and third trimesters (months 4 through 9 of pregnancy) don’t raise the risk of birth defects, stillbirths, or health problems shortly after birth, though they may increase the risk of early delivery. Researchers still don’t know if these children will have any long-term effects.
When a pregnant woman with early breast cancer needs chemo after surgery (adjuvant chemo), 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 some cases. These same treatment plans may also be used for women with more advanced cancer.
Chemo should not be given after 35 weeks of pregnancy or within 3 weeks of delivery because it can lower 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 before childbirth.
Radiation therapy
Radiation therapy to the breast is often used after breast-conserving surgeries (lumpectomy or partial mastectomy) to help 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. Because of this, doctors don’t use radiation treatment during pregnancy.
Pregnant women who choose lumpectomy or partial mastectomy may be able to have surgery during pregnancy and then wait until after the baby is born to get radiation therapy. But this treatment approach has not been well-studied. Waiting too long to start radiation can increase the chance of the cancer coming back.
Hormone therapy
Hormone therapy is often used as adjuvant treatment after surgery or as treatment for advanced breast cancer. Tamoxifen is the drug is given to younger (premenopausal) women, but it’s not used in pregnant women because it’s been linked to a high rate of birth defects.
Aromatase inhibitors, such as anastrozole, letrozole, and exemestane, are also sometimes used in women who are past menopause to help keep cancer from coming back. These drugs aren’t expected to work in younger women, and they aren’t safe to use during pregnancy.
Hormone therapy should not be used during pregnancy because it can affect the fetus. It should be delayed until after the woman has given birth.
Targeted therapy
Drugs that target HER2, like trastuzumab (Herceptin®), pertuzumab (Perjeta®), ado-trastuzumab emtansine (Kadcyla™) and lapatinib (Tykerb®), are an important part of the treatment of HER2-positive breast cancers in women who aren’t pregnant. Trastuzumab is used as a part of adjuvant treatment after surgery, pertuzumab can be used with trastuzumab before surgery, and all of these drugs can be useful in treating advanced cancer. But based on animal studies and reports of women who were treated during pregnancy, none of these drugs are considered safe for the fetus if taken during pregnancy.
Everolimus (Afinitor®) and bevacizumab (Avastin®) are also targeted drugs that can be used to treat advanced breast cancer. Again, neither of these drugs is safe to use during pregnancy.
If you’d like more information on a drug used in your treatment or a specific drug mentioned in this section, see our Guide to Cancer Drugs , or call us with the names of the medicines you’re taking.
Breastfeeding 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) breastfeeding.
If surgery is planned, stopping breastfeeding 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, hormone, and targeted therapy drugs can enter breast milk and be passed on to the baby. Breastfeeding isn’t recommended if the mother is getting chemo, hormone, or targeted therapy.
If you have questions, such as when it might be safe to start breastfeeding, be sure to talk with your health care team. If you plan to start back after you’ve stopped breastfeeding for a while, you will want to plan ahead. You may need extra help from breastfeeding 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 has breast cancer during her 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 health care team.
If you would like more information on breast cancer and its treatment, please read our document called Breast Cancer.
Survival rates after breast cancer during pregnancy
Pregnancy can make it harder to find, diagnose, and treat breast cancer. 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, but not all studies agree. A 2013 study looked at more than 300 women diagnosed during pregnancy. During the 5-year follow-up, researchers reported comparable survival in women at the same stage whose breast cancer was found when they weren’t pregnant. Disease-free survival tended to be slightly shorter in the pregnant women.
Some doctors believe that ending the pregnancy may help slow the course of more advanced breast cancers, and they may recommend that for some women with advanced breast cancer. It’s hard to do research in this area, and good, unbiased studies don’t exist. Ending the pregnancy makes treatment simpler, but older studies that looked at pregnant women have reportedly not found that ending the pregnancy improves a woman’s overall survival or cancer outcome. Of note, there were some flaws that could have biased the outcomes of these studies. For example, the women who had more advanced disease were more likely to end their pregnancies. More recent studies on this can’t be found in the available medical literature, and it’s hard to know if outcomes would be different with more modern treatments.
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. Finally, there are no reports showing that breast cancer itself can harm the baby.
Getting pregnant after treatment for breast cancer
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. The best time to talk with your doctor about fertility is before starting breast cancer treatment.
Because many breast cancers are sensitive to estrogen, there has been concern that if a woman has been treated for breast cancer, high hormone levels during pregnancy might increase the chance of the cancer coming back. Studies have shown, though, that pregnancy does not increase the risk of the cancer coming back after successful treatment.
Still, many doctors advise breast cancer survivors to wait at least 2 years after all treatment has finished 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. 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, or targeted therapy, such as trastuzumab, should talk with their doctors before trying to become pregnant. These drugs could affect a growing fetus, and stopping them early can increase the risk of the cancer coming back. (See the sections called “Hormone therapy” and “Targeted 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’s also no proof that breastfeeding after breast cancer treatment shortens survival. But women who have had breast surgery and/or radiation should know that they may have problems breastfeeding from the affected breast. Studies have shown reduced milk production in that breast as well as structural changes that can make it difficult and painful for the baby to latch onto the breast.
Another important thing to remember is that chemotherapy for breast cancer also 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 chance of getting pregnant after breast cancer treatment. For more about how cancer treatment can affect fertility, see our document called Fertility and Women With Cancer.
All women who have or have had had breast cancer and are thinking about having children should talk with their doctors about how treatment could affect their chances for pregnancy. This discussion should also cover the risk of the cancer coming back. In many cases, counseling can help women sort through the choices that come with surviving breast cancer and planning a pregnancy.