Introduction: Monochorionic diamniotic twin pregnancies represent a rare event associated with an extremely rare complication of the spontaneous rupture of the dividing membrane between the amniotic sacs. Once this rupture appears, the pregnancy becomes functionally a monoamniotic pregnancy, with a high risk of developing umbilical cord entanglement (up to 50%) and a supplementary rise in the perinatal mortality (up to 70%).

Method: This literature review includes 10 highly selected cases of spontaneous septostomy, respectively patients with diamniotic pregnancy who didn’t have any invasive procedures, included between 2012-2024.

Results: In 80% of the identified cases, the diagnosis was established antenatally, during the ultrasound examination from the second trimester, between 24-28 weeks of gestation. One of the most important and severe complications is represented by the umbilical cord entanglement (60%). The age of gestation at the moment of delivery varied between 24-37 weeks, with the majority being over 32 weeks. The chosen method of delivery, in the majority of cases was by cesarean section. There are established risk factors for the eventuality of a septostomy, also the ultrasound elements that can facilitate the diagnostic, maintaining the necessity of an anatomopathological confirmation.

Conclusion: During the monochorionic diamniotic pregnancy, the spontaneous rupture of the dividing membrane is an extremely rare event with a high difficulty of diagnosis antenatally. Once the diagnostic was established, the pregnancy should benefit from a management similar to a monochorionic pregnancy.

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