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How to Treat Pregnant Women. Breast Cancer Guidelines

Other Considerations
Jennifer Griggs
Breast Medical Oncologist
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December 13, 2022
How to Treat Pregnant Women. Breast Cancer Guidelines

Although it’s uncommon, some women are diagnosed with breast cancer during pregnancy or shortly after giving birth. If this is the case for you, your medical team will do everything they can to support you and make your baby’s health a top priority.

Breast cancer itself does not appear to harm an unborn baby. 1 Your medical team will know how to adjust your treatments to protect the baby while treating the cancer and as you make decisions about your own health. Treatments will vary depending on how far along you are in your pregnancy and the location and size of your tumor. 2

Coping with a breast cancer diagnosis is already difficult, and concern for your baby’s health adds to this emotional burden. Read on to learn more about how your medical team can give you the breast cancer treatment you need while keeping your baby safe and healthy.

Pregnancy-related breast cancer

Cancer found during pregnancy, while you’re breastfeeding, or up to a year postpartum is called pregnancy-related breast cancer. 3 Breast cancer affects 1 in every 3,000 pregnant women and occurs most often between 32 and 38 years of age. Researchers think this number may increase as more women choose to have children later in life. 1

Breast cancer cells do not get passed to an unborn baby. 1 There is no need to end a pregnancy due to a breast cancer diagnosis. Experts say that ending a pregnancy is not likely to improve a mother’s chance of survival. 1

An obstetrician specializing in high-risk pregnancies can work with your cancer care team to help you manage both your breast cancer and pregnancy at the same time. You can ask for a referral if you haven’t been referred to a high-risk obstetrician (OB).

Detection of breast cancer during pregnancy

Breast cancer can be harder to detect in pregnant women than in non-pregnant women. Hormonal changes during pregnancy and postpartum can change how breasts look and feel. Breasts may increase in size, and tissue may become denser. These changes can make detecting lumps through breast exams or mammograms more difficult. (1,4)

As a result, breast cancer may be diagnosed later in pregnant women than in non-pregnant women. The National Cancer Institute recommends that women regularly perform breast self-exams and receive clinical breast exams at checkups throughout pregnancy and postpartum. 1

Imaging tests

It’s generally safe for pregnant women to receive mammograms because the radiation is focused on the breasts. The abdominal and pelvic areas are protected from radiation with a lead shield. Although it’s a small amount, some radiation can reach the unborn baby during a mammogram.5 There is also a chance that a mammogram may appear negative for cancer when there is cancer present (a false negative). (1,4)

Breast ultrasounds do not use radiation and are considered safe for pregnant women and fetuses. 4 We do not recommend that pregnant women receive PET scans, CT scans, or bone scans to detect cancer because these tests may cause harm to the unborn baby through radiation exposure. If you need one of these scans, the imaging technicians will do everything they can to protect your reproductive organs. Diagnostic tests done later in pregnancy, after the major organs have formed and matured, do not carry the same risks.

MRIs are also not recommended during pregnancy because gadolinium, the material used in MRIs, has the potential to cross the placenta and harm the baby. 5 MRIs are considered lower risk for nursing mothers because only small doses of the material make it into breast milk. Mothers may also use alternative feeding methods for a short period after an MRI to avoid exposure through breast milk altogether. 4


Two types of biopsies may be used to detect cancer in pregnant women.

  • Core needle biopsies involve numbing a small area of the breast and using a small needle to extract breast tissue samples. This biopsy poses no risk to the baby and is the most common type used. 5
  • Surgical biopsies involve making a small cut in the breast to remove larger samples. Because this type of biopsy is done while the patient is under anesthesia, there is a small risk to the baby from the anesthesia. 5


Staging is the process of finding out how large a tumor is and whether the cancer has spread. This determines what stage of cancer you have (I, II, III, or IV). We do not do staging tests in people with Stage 0, or ductal carcinoma in situ. Similarly, unless someone has symptoms of spread (such as bone pain), we do not do staging scans in people with Stages I or II breast cancer.

During pregnancy, we might use ultrasound or chest x-rays during staging. Chest x-rays use small amounts of radiation. They are generally considered safe during pregnancy because the X-ray beam is focused on the chest and does not reach reproductive organs.6 As with mammograms, the abdomen and pelvis are protected with a lead shield. 5


Breast cancer treatment for pregnant women is similar to treatment for non-pregnant women with some changes made to protect the mother and unborn child. Your medical team may include a medical oncologist, surgeon, radiation oncologist, high-risk obstetrician, pediatrician, or other medical specialists. These care team members will work together to ensure that you and your baby get the best possible treatment.

You may also wish to talk with a counselor, psychologist, social worker, or other specialist who can help you care for your mental health during this challenging time. 2 Changing hormone levels during pregnancy and postpartum can affect your mood and energy levels.

It’s not uncommon for women to feel symptoms of anxiety and depression before and after giving birth even without a cancer diagnosis. Cancer treatments can also affect how you feel physically and emotionally. Give yourself permission to prioritize your own needs and reach out for support. Your family, friends, and care team are all here to support you. If your family is not supportive, reach out to the social worker on your team to help you find support in other places.


As with people who aren’t pregnant, surgery is often the first step in treating pregnant patients.7 It is considered safe to have breast cancer surgery during all three trimesters of pregnancy. 4

Being under anesthesia can pose some risks to the baby. Your surgeon, anesthesiologist, and obstetrician can work together to determine the safest time for you to have surgery and what anesthesia drugs are the safest to use. If you have surgery later on in your pregnancy, your obstetrician may attend to help make sure your baby is doing well during surgery. 2

The type of surgery you have depends on the size and location of your tumor and how far the cancer has spread. You may have a modified radical mastectomy, which is the total removal of the breast tissue and most of the lymph nodes under the arm.1 Or, you may have a lumpectomy (also called breast-conserving surgery), which is the partial removal of the breast tissue. 8

Axillary lymph node dissection is often standard treatment for pregnant women and can be performed along with a lumpectomy.(2,4) This is the removal of lymph node(s) to determine if cancer has spread to your lymph system. 8 Unless the lymph nodes are palpable, you will most likely have a sentinel lymph node biopsy (SLNB). While the surgeon removes fewer nodes during an SLNB, experts are concerned that the blue dye used in the procedure may harm the baby. Therefore, experts recommend that SNLB is only performed later in pregnancy and that the blue dye is not used during the procedure. 2

Some people choose to have breast reconstruction surgery to rebuild their breast tissue after the cancer is removed.8 Reconstruction surgery can sometimes be done at the same time the cancer is removed, but this can make the operation longer. It is likely that delayed reconstruction will be recommended to avoid a lengthy reconstructive surgery. 9 This is particularly the case if you are using your own abdominal tissue to have reconstruction.


Chemotherapy is generally considered safe during the second and third trimesters of pregnancy.3 Chemotherapy is not given during the first trimester because it can harm the baby’s development, and the risk of miscarriage is higher.(2-3) Research shows that when given in the second or third trimester, most chemotherapy drugs given to treat breast cancer do not cause birth defects or other health problems for the baby. Long-term data show no relationship between fetal chemotherapy exposure and the development of various diseases and neurological disorders. 12

There is a chance that these drugs may cause the baby to be born earlier or have a low birth weight.(1,2) However, one recent study showed no significant difference in birth weight or the number of early births between babies who were exposed to chemotherapy and those who were not. 13

Some pregnant women have chemotherapy before surgery to reduce the tumor size, reduce any disease in the lymph nodes, and allow the baby to mature before surgery. This may reduce the time you’ll be under anesthesia during the operation.

Chemotherapy is generally not given within three to four weeks of giving birth because it can increase the risk of infection or bleeding during delivery. 9 If you are diagnosed with cancer in your third trimester, you may be able to wait until after you’ve given birth to start chemotherapy. In some cases, doctors induce labor early so treatment can start sooner. 2 Labor will not be induced until the baby has developed to the point where it is safe to deliver early.

Breastfeeding is not recommended during chemotherapy because the drugs may pass into the breast milk and harm the baby.3 Some people are able to express (pump) and store milk before starting chemotherapy. This milk can be given to the baby to help it get the benefits of early breast milk.


High doses of radiation are used during radiation therapy, which can harm an unborn baby. Radiation during pregnancy may cause miscarriage or birth defects and increase the chances that the child may have cancer later in their lifetime. 2 Therefore, if possible, we delay radiation therapy until after the baby is born. 1

Waiting too long to start radiation therapy after surgery may increase the chance that the cancer will come back. People with Stage I or Stage II cancer may be able to delay radiation therapy until after the baby is born, but people who have Stage III or IV cancer may need it sooner. If radiation therapy needs to be given during pregnancy, waiting until after the first three months of pregnancy can help protect the baby. 1 As with chemotherapy, you and your doctor may decide to induce labor early so that you can start radiation therapy sooner.

For nursing mothers, radiation therapy may impact the ability to produce milk in the treated breast. One side effect of radiation is skin toxicity. The skin of the breast may be red, swollen, painful, and warm to the touch. Breastfeeding from a treated breast may make skin toxicity worse and lead to an infection known as mastitis. 10 You may be able to breastfeed from your non-treated breast. 11

Endocrine therapy

Cancers that are hormone receptor-positive (HR-positive) can be treated with endocrine therapy (sometimes called hormonal therapy). Endocrine therapy is not recommended during pregnancy because the drugs used can negatively affect the baby. 2

One common drug used in endocrine therapy is tamoxifen. Research shows tamoxifen may cause birth defects or other health problems in unborn babies. 4

If your cancer is HR-positive, your doctor may recommend starting endocrine therapy after giving birth.2 It is also not recommended to breastfeed while receiving endocrine therapy because the drugs used may enter the breast milk and harm the baby. 3

Targeted therapy

Because targeted therapies are relatively new, we don’t know much about how these drugs can affect unborn babies. Currently, the consensus is that targeted therapy should not be given during pregnancy. (2,9)

One drug used to treat HER2-positive breast cancer is trastuzumab. Trastuzumab targets a protein called human epidermal growth factor receptor 2 (HER2). Research shows that using trastuzumab during pregnancy is associated with low amniotic fluid and respiratory and heart problems in unborn babies. 4

Because of these observations and the unknown effects of other targeted therapy drugs, it’s recommended that targeted therapy be delayed until after the baby is born. (3,4)


While breast cancer does not appear to harm unborn babies, some standard breast cancer treatments and diagnostic tests can potentially cause harm during pregnancy. Delaying certain treatments until after birth and making other adjustments can protect your baby. Your obstetrician and cancer care team can work together to develop the safest possible treatment plan for you and your baby.


  1. Breast cancer treatment during pregnancy (PDQ®)–patient version. National Cancer Institute. Published April 14, 2022. Accessed November 27, 2022.
  1. Treating breast cancer during pregnancy. American Cancer Society. Published October 27, 2021. Accessed November 27, 2022.
  1. Potter M. Pregnancy-related breast cancer. Johns Hopkins Kimmel Cancer Center. Published April 2, 2018. Accessed November 27, 2022.
  1. Martínez MT, Bermejo B, Hernando C, Gambardella V, Cejalvo JM, Lluch A. Breast cancer in pregnant patients: A review of the literature. European Journal of Obstetrics & Gynecology and Reproductive Biology. 2018;230:222-227. doi:10.1016/j.ejogrb.2018.04.029
  1. Finding breast cancer during pregnancy. American Cancer Society. Published January 14, 2022. Accessed November 27, 2022.
  1. Tobah YB. X-ray during pregnancy: Is it safe? Mayo Clinic. Published March 19, 2022. Accessed November 27, 2022.
  1. Breast cancer during pregnancy. National Breast Cancer Foundation. Published May 18, 2022. Accessed November 27, 2022.
  1. Breast cancer surgery: Types, procedure & recovery. Cleveland Clinic. Published May 18, 2022. Accessed October 17, 2022.
  1. Breast cancer during pregnancy. Cancer Research UK. Published March 10, 2021. Accessed November 27, 2022.
  1. Shachar SS, Gallagher K, McGuire K, et al. Multidisciplinary management of breast cancer during pregnancy. The Oncologist. 2017;22(3):324-334.doi:10.1634/theoncologist.2016-0208
  1. Breastfeeding and breast cancer treatment. Breast Cancer Now. Published March 8, 2022. Accessed November 27, 2022.
  1. Greiber IK, Viuff JH, Storgaard L, et al. Long-term morbidity and mortality in children after in utero exposure to maternal cancer. Journal of Clinical Oncology. 2022;40(34):3975-3984. doi:10.1200/jco.22.00599
  1. YP Z, J D, XW Z, J L, Y S. Maternal and neonatal outcomes of cancer during pregnancy: A multi-center Observational study. Journal of Cancer. Published October 3, 2019. Accessed November 29, 2022.
About The Blog Author
A long-time practicing oncologist and professor at the University of Michigan, Jennifer has received several awards for her medical excellence and published over 150 original research articles as well as numerous editorials and book chapters. She is also a speaker and advocate, committed to improving the quality of medical care and reducing the barriers to equity among the disenfranchised.
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