PURPOSE: The rare association between breast cancer and pregnancy means that few oncologists gain an expertise in this area. In particular, there are few published data concerning the use of chemotherapy for breast cancer during pregnancy. In this retrospective case series, we describe the experiences of five hospitals in London, United Kingdom, and how they manage this condition. PATIENTS AND METHODS: Retrospective searches were performed at five London hospitals in order to identify women who received chemotherapy for breast cancer while pregnant. RESULTS: Twenty-eight women were identified who had received chemotherapy for breast cancer during pregnancy. Twenty-four women received adjuvant or neoadjuvant chemotherapy for early breast cancer, and four women received palliative chemotherapy for metastatic disease. A total of 116 cycles of chemotherapy were administered during pregnancy. Sixteen women were treated with anthracycline-based chemotherapy and 12 received cyclophosphamide, methotrexate, and fluorouracil. All but one of the women were treated after the first trimester. One spontaneous abortion occurred in the woman treated during her first trimester; otherwise, there were no serious adverse consequences for the mothers or neonates. CONCLUSION: These data provide evidence that in terms of peripartum complications and immediate fetal outcome, chemotherapy can be safely administered to women during the second and third trimesters of pregnancy.