Pregnancy and Breast Cancer: Risks, Benefits, and Considerations

For young patients with breast cancer, pregnancy is not only possible, but could be beneficial, shared Don S. Dizon, MD, FACP, FASCO, in a presentation on the safety and considerations of pregnancy and breast cancer at the 43^rd Annual Miami Breast Cancer Conference’s nursing track.¹

According to Dizon’s presentation, 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 vs non-luminal subtypes.

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

Dizon emphasized the need for referrals 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 2 years from the time of diagnosis to try to conceive.

Patients who are taking tamoxifen should hold off for an additional 3 months after ceasing treatment, and those taking trastuzumab (Herceptin) should wait 7 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% (95% CI, 94.1%-99.3%) 5-year overall survival rate for women who conceived 6 months or more after a breast cancer diagnosis, compared with 87.5% (95% CI, 86.5%-88.4%) in those who did not have pregnancy during cancer and 82.1% (95% CI, 78.3%-85.9%) for those with pregnancy-associated breast cancer (age-adjusted HR, 0.22; 95% CI, 0.10-0.49).²

Further,Dizon cited data published in Cancer in 2018 that showed that patients who conceived 1 year or sooner after starting chemotherapy for any cancer had a greater risk of preterm birth, with a relative risk (RR) of 1.9 (95% CI, 1.3-2.7) for those who received chemotherapy alone and an RR of 2.4 (95% CI, 1.6-3.6) in those who received chemoradiation.³ Those who conceived 1 year or longer after initiating chemotherapy with or without radiation or those who conceived 2 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% (95% CI, 6.3%-11.6%) had a breast cancer event in 3 years.⁴

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 (95% CI, 2.2-10.3) 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.⁵

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:

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

With HER2-targeting therapies:

• Ado-trastuzumab emtansine (T-DM1; Kadcyla): cardiovascular malformations
• Lapatinib (Tykerb): intrauterine growth retardation; pregnancy complications
• Trastuzumab: fetal malformations; congenital respiratory tract malformation; genetic disorder; oligohydramnios; neonatal kidney failure
• Pertuzumab (Perjeta): congenital respiratory tract malformation; oligohydramnios

So, What Should I Tell Patients?

Dizon urged nurses and APPs to let patients know that pregnancy is possible, even if patients come with a preconceived notion that it is not. Patients should prepare by considering factors such as timing and potential complications or birth defects. Patients should understand the importance of resuming cancer therapy after pregnancy, especially those with ER-positive disease receiving endocrine therapy.

References

1. Dizon DS. Pregnancy and breast cancer: key considerations and counseling pearls. Presented at the 43rd Miami Breast Cancer Conference; March 5-8, 2026
2. Iqbal J, Amir E, Rochon PA, Giannakeas V, Sun P, Narod SA. Association of the timing of pregnancy with survival in women with breast cancer. JAMA Oncol. 2017;3(5):659-665. doi:10.1001/jamaoncol.2017.0248
3. Hartnett KP, Mertens AC, Kramer MR, et al. Pregnancy after cancer: Does timing of conception affect infant health? Cancer. 2018;124(22):4401-4407. doi:10.1002/cncr.31732
4. Partridge AH, Niman SM, Ruggeri M, et al. Interrupting endocrine therapy to attempt pregnancy after breast cancer. N Engl J Med. 2023;388(18):1645-1656. doi:10.1056/NEJMoa2212856
5. Sankila R, Heinävaara S, Hakulinen T. Survival of breast cancer patients after subsequent term pregnancy: “healthy mother effect.” Am J Obstet Gynecol. 1994;170(3):818-823. doi:10.1016/s0002-9378(94)70290-x