Breast Cancer and Pregnancy: What to Know About Risks and Timing

Pregnancy can be not only possible but beneficial, as one expert recently explained.

Dr. Don S. Dizon delivered a presentation on the safety and considerations of pregnancy at the 43^rd Annual Miami Breast Cancer Conference, as part of the conference’s nursing track, in which he stated that breast cancer impacts approximately 1 in 50 women before age 50, and it is most likely to present as a rapidly growing mass. In young women, breast cancer diagnoses tend to be later in stage, of a higher grade and negative for hormone receptors.

More aggressive subtypes, such as basal-like and HER2-positive, are more common in younger women, and patients face a higher risk of death with early-stage luminal breast cancers versus non-luminal subtypes.

What Options Exist for Patients With Breast Cancer Who Want to Conceive?

Dizon emphasized the need for referrals to fertility counseling early on in a patient’s treatment if the patient is interested in pursuing fertility preservation. Options are not limited to ovarian stimulation: others include ovarian tissue cryopreservation as well as immature oocyte retrieval and in vitro maturation.

Alternatively, patients may be interested in pursuing alternatives to traditional pregnancy, such as donor oocyte or embryo, having a surrogate gestational carrier or adoption.

Timing Is Everything With Pregnancy and Breast Cancer

Dizon shared that timing is crucial when looking at pregnancy and breast cancer. Patients with breast cancer should avoid unplanned pregnancy and wait for two years from the time of diagnosis to try to conceive.

Patients who are taking Nolvadex (tamoxifen) should hold off for an additional three months after ceasing treatment, and those taking Herceptin (trastuzumab) should wait seven months after treatment discontinuation.

If patients decide to conceive after breast cancer, safety of both lives should be considered. Dizon cited research published in JAMA Oncology in 2017 which demonstrated a 96.7% five-year overall survival rate for women who conceived six months or more after a breast cancer diagnosis, compared with 87.5% in those who did not have pregnancy during cancer and 82.1% for those with pregnancy-associated breast cancer.

Further,Dizon cited data published in Cancer in 2018 that showed that patients who conceived one year or sooner after starting chemotherapy for any cancer had a greater risk of preterm birth. Those who conceived one year or longer after initiating chemotherapy with or without radiation or those who conceived two years or longer after chemoradiation did not face the same risk.

Of note, Dizon cited research published in The New England Journal of Medicine in 2023 that demonstrated that of patients with breast cancer who interrupted treatment with adjuvant endocrine therapy to attempt pregnancy, only 8.9% had a breast cancer event in three years.

Dizon noted research published in the American Journal of Obstetrics and Gynecology in 1994 that observed a “healthy mother effect,” where women with breast cancer who did not deliver children had a risk of death 4.8 times that of those who did deliver children 10 months or longer after diagnosis, with patients matched for stage, age and year of breast cancer diagnosis.

Weighing the Risks of Pregnancy With a Breast Cancer Diagnosis

While pregnancy with a breast cancer diagnosis is possible and may even benefit survival for some, Dizon highlighted some of the risks associated with several treatment groups.

With systemic treatment:

• Cyclophosphamide: skeletal, palate, limb or eye malformations; miscarriage; fetal growth retardation; bone marrow hypoplasia
• Platinum-based chemotherapy: oligohydramnios; intrauterine growth restriction; preterm birth; hearing loss
• Taxanes: myelosuppression; pyloric stenosis

With HER2-targeting therapies:

• Kadcyla (ado-trastuzumab emtansine; T-DM1): cardiovascular malformations
• Tykerb (lapatinib): intrauterine growth retardation; pregnancy complications
• Herceptin: fetal malformations; congenital respiratory tract malformation; genetic disorder; oligohydramnios; neonatal kidney failure
• Perjeta (pertuzumab): congenital respiratory tract malformation; oligohydramnios

References

1. “Pregnancy and breast cancer: key considerations and counseling pearls” by Dr. Don S. Dizon, presented at the 43rd Miami Breast Cancer Conference; March 5-8, 2026
2. “Association of the timing of pregnancy with survival in women with breast cancer,” By Dr. Javaid Iqbal, et al., JAMA Oncol.
3. “Pregnancy after cancer: Does timing of conception affect infant health?” by Kathleen P. Hartnett et al., Cancer.
4. “Interrupting endocrine therapy to attempt pregnancy after breast cancer” by Dr. Ann H. Patridge et al., N Engl J Med.
5. Survival of breast cancer patients after subsequent term pregnancy: “healthy mother effect,” by Dr. Risto Sankila, et al., Am J Obstet Gynecol.

For more news on cancer updates, research and education, don’t forget to subscribe to CURE®’s newsletters here.