Breast Cancer Treatment During Pregnancy
While breast cancer during pregnancy or soon afterwards is rare, it’s important to understand your choices. Breast Cancer Foundation NZ explain your options in this article
6 min read
Pregnancy – Expert Article by 
Breast Cancer Treatment During Pregnancy
Firstly, let us reassure you that finding breast lumps during pregnancy and breastfeeding isn’t unusual – they’re usually a cyst or abscess, or due to engorgement of the milk ducts or mastitis. However, check in with your doctor about a lump that doesn’t go away, that grows in size, causes dimpling or “orange peel” skin, or doesn’t move within the breast tissue when you press on it. Your GP can refer you for further assessment. In a minority of cases, breast cancer may be diagnosed. We are going to discuss breast cancer treatment while pregnant or breastfeeding below.
Diagnosis of breast cancer while pregnant or breastfeeding
Breast cancer diagnosed during pregnancy, breastfeeding or in the first year post-delivery is rare, occurring in one in every 3000 pregnancies. It is known as pregnancy-associated breast cancer. It is sometimes diagnosed at a later stage because changes in the breast during pregnancy and breastfeeding can make the cancer more difficult to detect.
Pregnant women are diagnosed in the normal way, except that MRI is not usually recommended for women in the first trimester (from conception to 12 weeks). Ultrasound is safe and will not hurt your unborn baby, and shielding will be used to protect your abdomen during a mammogram. The cancer itself will not affect your baby’s development.
The treatment you receive will depend on the type of breast cancer you have and the trimester of your pregnancy. Most women are able to undergo treatment while pregnant, without harming the unborn baby.
Termination of pregnancy is not usually recommended, as it hasn’t been shown to improve outcomes for women. However, if chemotherapy is required during the first trimester or for aggressive or advanced disease, termination may be discussed with you. Terminating the pregnancy is a very personal decision and can only be made by you and your partner following a full discussion with your cancer treatment team and your obstetrician.
Treatment during pregnancy
The following is an overview only – all treatment decisions should be made in consultation with your specialist team.
If you are nearing the end of your pregnancy, your team may recommend delaying any treatment until after birth.
Breast surgery to remove the tumour can be performed at any time during pregnancy. Due to the risk radiation treatment poses to your unborn child, a full mastectomy will most likely be recommended, because breast-conserving surgery (also known as a partial mastectomy or lumpectomy) would require follow-up radiotherapy. However, if you’re in the third trimester, breast-conserving surgery may be an option, with radiotherapy starting after the baby is born.
Breast reconstruction is an option following mastectomy, but is only offered as a delayed procedure due to the length of the operation, and the recovery time needed.
Chemotherapy can be used during pregnancy but is not given during the first trimester, as it could harm your developing baby. Studies have shown, however, that several types of chemotherapy can be given in the second and third trimesters without harming the baby. Chemotherapy is usually stopped three weeks prior to your due date to avoid complications at birth (eg. infection, for which the risk is higher during chemotherapy) but can be continued after birth.
Radiotherapy is often given after chemotherapy, but would not begin until after birth. Radiotherapy is not recommended at any time during pregnancy as it poses a risk to your unborn baby, even when it’s given in low doses. It may be possible to delay radiotherapy until after birth – your specialists will discuss this with you.
Hormone blocking therapies like tamoxifen are not given during pregnancy, but can be taken after birth, if appropriate for your type of cancer. The targeted therapy Herceptin (for HER2 positive cancer) is not given during pregnancy but is used after birth if needed.
Breast cancer is most treatable when it's found early - don't wait
Use our tool to learn what you can do at your age to be breast aware!
From age 20, it’s important to know the look and feel of your breasts, and show any changes to your doctor. From age 40, we recommend you start regular mammograms.
What you should do depends on your age. Pop your age into our tool and we will show you what you can do and explain risk factors.
Delivering your baby
Most women diagnosed during pregnancy complete their pregnancy to full term and experience no additional difficulties at delivery. Caesarean section is avoided when possible as it carries a heightened risk of infection, especially if you have been having chemotherapy, which affects the immune system.
After the birth
Having chemotherapy after birth or starting radiotherapy can also present challenges for a new mother. You will be advised not to breastfeed during treatment, as the drugs can pass through the bloodstream and into breast milk. Talk to your oncologist about whether or not breastfeeding is safe with the treatments you’re receiving.
Caring for a newborn baby while undergoing breast cancer treatment is demanding, both physically and emotionally. Talk to your healthcare team to see if you might be eligible for any assistance. It’s important that you are able to get adequate rest, so talk to family and friends about practical support they could offer.
Expert Profile: Breast Cancer Foundation NZ
Working towards a future where no one dies from breast cancer
Breast Cancer Foundation New Zealand is a not-for-profit charitable trust, relentlessly pushing for new frontiers in early detection, treatment and support relating to breast cancer. This includes funding the latest research and technology and breaking down the barriers that stop every eligible woman getting her mammogram.
BCFNZ tirelessly support all Kiwis with education about breast awareness, screening mammograms, breast cancer risk and breast health, including women and men in remote areas, and ethnic groups with poorer breast cancer outcomes.
Think about making a donation or head over to their website which is packed full of information and resources.
