To explore the monitoring and prognosis of pregnancies complicated with breast cancer.

A retrospective analysis was conducted on 34 patients with pregnancy complicated with breast cancer who were treated at our hospital from January 1, 2006 to March 31, 2025. Their clinical characteristics, pregnancy outcomes, and prognosis were analyzed.

The 34 patients ranged in age from 23 to 42 years, with a mean age of 32.56±5.58 years. Most cases were diagnosed in the second and third trimesters (28 cases, 82.35%), of which 11 were advanced breast cancer. The double-negative rate (both progesterone receptor and estrogen receptor negative) was 35.49% (11 cases). Among the 34 patients, 28 chose to continue their pregnancy. Of these 28 patients, 3 underwent radical mastectomy during pregnancy: one delivered at term, and two delivered at 33 weeks and 31^{+ 3} weeks of gestation, respectively. 2 patients received surgery combined with chemotherapy and both delivered at term. 15 patients received chemotherapy alone during pregnancy, all using the EC regimen (epirubicin + cyclophosphamide), with an average prolongation of gestation of 13.30±5.52 weeks and a mean gestational age at delivery of 36.35±1.78 weeks. 8 patients received no treatment. Newborns were followed up and showed normal growth and development. After induced labor or delivery, all patients received comprehensive treatment for breast cancer. To date, 28 patients have survived, three were lost to follow-up, and three died due to systemic metastasis.

Surgery and/or chemotherapy are relatively safe for pregnancies complicated with breast cancer during the second and third trimesters, and the neonatal outcomes are favorable.