Background: Hemoperitoneum resulting from spontaneous rupture of the uterine vessels in pregnancy is rare and associated with high maternal and fetal mortality.
Case: A woman presented with acute abdominal pain and hypovolemic shock at 20 weeks of gestation. Immediate laparotomy revealed massive hemoperitoneum resulting from spontaneous rupture of the left uterine vessels associated with a left adnexal mass consisting of decidualized endometriosis.