A 36-year-old female diagnosed of breast cancer was treated with surgery, chemotherapy, radiotherapy and goserelin. After 17 months of uninterrupted therapy with this LHRH analogue at hormone suppressive doses, a 16-week gestation foetus was detected and the treatment was withdrawn. Although the drug was administered throughout the first 4 months of pregnancy it resulted in the term delivery of a healthy infant, and no foetal adverse effects were detected. A review of the influence of hormonal treatment for breast cancer on fertility and birth defects has been performed.