Breast Cancer During Pregnancy

Breast cancer rarely occurs during pregnancy, with breast cancer occurring in an estimated 1 out of every 3,000 pregnancies.1 While cancer in any form is rare during pregnancy, breast cancer is the most common cancer diagnosed during pregnancy. When breast cancer is diagnosed during pregnancy, it can be complicated for both the mother and the baby.2

Breast cancer during pregnancy occurs most often in women between the ages of 32 and 38, although it can occur in younger women.1Genetic mutations may account for many of these breast cancers. It is estimated that approximately 33% of breast cancers that occur in pregnant women in their 20’s are due to a BRCA mutation, and approximately 22% of breast cancers that occur in pregnant women in their 30’s are due to a BRCA mutation.3

Signs of advanced breast cancer in pregnant women

Breast cancer can be difficult to detect in pregnant or breastfeeding women, due to the breasts often becoming larger and/or lumpier, and potentially denser. These breast changes occur due to the hormone changes in pregnancy and can make it more challenging to find breast cancers when they are small.1

Common signs or symptoms of breast cancer during pregnancy include1:

  • A lump in the breast or underarm area
  • A change in breast size or shape
  • Dimples or puckering of the skin of the breast
  • The nipple turning inward
  • Fluid that is not breast milk, especially bloody fluid, leaking from the nipple
  • Scaly, red, or swollen breast or nipple

Delayed diagnosis

Many women who are diagnosed with breast cancer during pregnancy are in advanced stages of the disease when diagnosed, because signs of breast cancer may be difficult to detect due to the body’s changes during pregnancy.1,3

Diagnosing advanced breast cancer during pregnancy

To diagnose breast cancer during pregnancy, several tests may be used, including1,2:

  • Clinical breast exam - an exam where the doctor feels the breast tissue and under the arm
  • Mammogram - an x-ray taken of breast tissue while the breast is compressed between two plates (a lead shield can be placed over the abdomen to help protect the baby from any radiation)
  • Ultrasound - a screening that uses sound waves and can be helpful in distinguishing between fluid-filled cysts or solid lumps
  • Magnetic resonance imaging (MRI) - a scan that uses magnets and radio waves to create pictures of internal structures in the body
  • Computed tomography (CT) scan - a scan that uses special x-ray equipment to make cross-sectional views of the inside of the body (a lead shield can be placed over the abdomen to help protect the baby from any radiation)
  • Biopsy - a procedure in which cells or the tumor is removed from the body to be examined under a microscope

Treatment for advanced breast cancer during pregnancy

Treatment options for women with breast cancer during pregnancy are similar to other women with breast cancer, but treatment approaches for breast cancer during pregnancy must consider the health of both the mother and the baby. Some treatments, such as hormone therapy and targeted therapy, may be dangerous for the unborn child and are not given during pregnancy. Other treatments, including surgery, radiation, and chemotherapy, can potentially be given during pregnancy, although chemotherapy and radiation are not recommended during the first trimester (the first three months of pregnancy).1,2

In addition, women who are breastfeeding should not receive certain treatments because they can pass into breast milk and could harm a baby that is nursing. Women should not breastfeed while receiving treatment with chemotherapy medications.1

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Written by: Emily Downward | Last reviewed: December 2018.