Uterine rupture of cesarean scar related to spontaneous abortion in the first trimester

We report the case of a 31-year-old Japanese female diagnosed by transvaginal ultrasonography to have a spontaneous uterine rupture in the first trimester. Her condition was complicated by diabetes mellitus type 1. Her previous pregnancy had resulted in an emergency cesarean section by transverse incision of the lower uterine segment with single-layer suture at 37(+4) weeks of gestation. Transvaginal ultrasonography displayed both a gestational sac located in the anterior lower uterine segment and a defect in the uterine wall located at the site of the previous cesarean delivery scar. Pelvic magnetic resonance imaging showed that the uterine muscle layer was discontinuous and the gestational sac was almost outside the uterine cavity, accompanied by mild hemorrhaging within the endometrial cavity. The defect in the lower uterine wall was round in shape and was 3 cm in diameter. Since uterine ruptures can occur during all gestational periods, it is important to pay attention to the uterine wall where any cesarean incision was previously made.