Breast Cancer During and After Pregnancy

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“I assumed it was either milk or some changes in my mammary glands due to breastfeeding, I would have never believed [it was breast cancer].” At 35, Patricia, a mother of two, lived the anguish of a breast cancer diagnosis after pregnancy. While breast cancer during and after pregnancy is very rare (0.2%–3.8% of all Breast Cancer cases), it is the most common cancer among pregnant women.


Breast cancer during pregnancy is often diagnosed late due to the natural changes occurring in the breast tissue. Therefore, it is important to be aware of breast cancer signs during this period and to discuss any persistent observations with your doctor. To learn how to recognize potential signs of breast cancer, check out our Breast Observation Guide.

At the clinic, a triple assessment approach is usually used to make the diagnosis:

  1. Breast examination
  2. Ultrasound scan or mammography
  3. Core biopsy of tissue or Fine Needle Aspiration (FNA) of cell

These tests are known to be safe for both the mother and the baby. On the other hand, CT scans and MRI are rarely used, and many conditions apply.


While treatment of breast cancer during pregnancy is dictated by the cancer type and stage like other breast cancer cases, the pregnancy trimester at time of diagnosis is also an important consideration. The aim is to decide on the best possible treatment for the patient that is also safe for her baby.

The table below summarizes the recommended treatments, for non-metastatic cases, by pregnancy trimester (National Comprehensive Cancer Network (NCCN) 2018):

1Mastectomy or breast-conserving surgery. During the first trimester, mastectomies are recommended.
2Used for hormone-positive cancers only.
3There is evidence for a small increase in the risk of low birth weight and early delivery.

For patients diagnosed with a Her2-positive breast cancer, Her2-targeted therapy (such as Herceptin) is not recommended during pregnancy.

Termination of Pregnancy

Terminating a pregnancy due to a breast cancer diagnosis is rarely recommended as studies have shown that a full term pregnancy has no impact on breast cancer prognosis. That is to say, if a pregnant woman and a non-pregnant woman both presented with the same type of breast cancer, they have the same chances of survival.

There are three exceptions where terminating a pregnancy is recommended:

  • If breast cancer is diagnosed at an advanced stage (stage 3 or 4) during the first trimester
  • If the breast cancer type is very aggressive
  • When a woman’s survival is estimated to be shorter than the time of a full-term pregnancy

In each of the listed scenarios, the need for an immediate and more thorough treatment is the main reason for ending the pregnancy.


After surgery, breastfeeding remains possible from the unaffected breast, but only in certain situations. Patients undergoing chemotherapy, hormone therapy, radiotherapy, or targeted therapy are advised to stop (or not to start) breastfeeding.

Pregnancy AFTER Breast Cancer

Due to the potential effects of cancer treatments on fertility, pre-menopausal women who are diagnosed with breast cancer and wish to get pregnant in the future should discuss the available options with their healthcare provider before starting chemotherapy and/or hormone therapy. Women who remain fertile post-treatment can have children without any increased risk of birth defects or childhood illnesses. Importantly, having a child following Breast Cancer treatment does not increase the chances of disease recurrences. Patients with a metastatic Breast Cancer (stage 4) are advised to avoid pregnancy.

You are not alone

With how rare Breast Cancer during or after pregnancy is, affected women and their loved ones may feel alone and perhaps isolated. It may be helpful to share your questions or feelings with others. We encourage you to call our support line to speak with our clinical nurse: 1-877-990-7171, ext. 250.