Importance: Uterine rupture is defined as a nonsurgical disruption of all layers of the uterus. Most ruptures occur in the presence of a scar, usually secondary to a previous cesarean delivery. Rupture of an unscarred uterus is rare and is associated with severe maternal and neonatal outcomes.
Objective: To outline the literature on potential predisposing factors, clinical findings, and maternal and fetal outcomes of a rupture of an unscarred uterus.
Evidence acquisition: PubMed was searched for the phrases "uterine rupture," "unscarred," and "spontaneous." Individual case reports, retrospective case series, and review articles in English between 1983 and 2020 were included.
Results: We found 84 case reports in 79 articles. The mean maternal age was 29.3 (SD, 5.7) years; 38 women (45.2%) were nulliparous. Uterine rupture occurred in 37% of the women at term; in 9.9%, the gestational age was ≤12 weeks. The most common clinical presentations were abdominal pain (77.4%), signs of hypovolemic shock (36.9%), fetal distress (31%), and vaginal bleeding (22.6%). The most common risk factors were the use of uterotonic drugs for induction or augmentation of labor and a prior curettage procedure. The most frequently ruptured site was the body of the uterus. Hysterectomy managed 36.9% of the ruptures. Four women died (4.8%). Perinatal mortality was 50.6%. Perinatal death was higher in developing than developed countries.
Conclusions and relevance: Although rare, spontaneous rupture of the unscarred uterus has serious consequences to the mother and the fetus and should be included in the differential diagnosis of acute abdomen in pregnancy.