Spontaneous haemoperitoneum in pregnancy has been associated with endometriosis. More women with endometriosis get pregnant due to improved fertility treatment and little is known of their risk of obstetrical complications. We report a case of a pregnant woman with a history of endometriosis who was admitted in gestational week 28 with spontaneous haemoperitoneum. We performed an emergency caesarean section and found multiple varicosities on the surface of uterus with active bleeding. Further knowledge on complications in pregnant women with endometriosis is needed.