Leiomyoma of the placenta is uncommon. We present a leiomyoma of the fetal membranes that was incidentally discovered on examination of a spontaneously expulsed placenta following Caesarean section. Although it is an uncommon entity, it is known that leiomyomas may arise from the vasculature nourishing the fetal membranes.. The baby was male and genetic studies were performed to detect Y chromosome in tumoral tissue. Polymerase chain reaction technique demonstrated Y chromosome in placental tissue but not in tumour tissue. Thus the tumour was finally diagnosed as incorporated benign uterine leiomyoma. (C) 2003 Elsevier Science Ltd. All rights reserved.