We report a case of spontaneous rupture of unscarred uterus, during labour and under epidural analgesia in a 43 year-old patient at her third pregnancy and third delivery. The tear was vertical and took place on the left postero-lateral side of the uterus, occurring in the whole height of the lower segment and overlapping towards the uterine corpus and cervix. Analysis of medical, surgical, gynaecological and obstetrical past history has displayed no predisposing factors explaining this rare occurrence. This clinical case reminds us that spontaneous rupture is always possible even on an unscarred uterus.