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.

Camelia Constantinescu is a teaching assistant with a Ph.D. in medical sciences since 1998 granted by the “Carol Davila” University of Medicine and Pharmacy, Bucharest, Romania, attending physician in obstetrics - gynaecology, with main practice focused on the field of maternal foetal medicine and minimal invasive gynaecological surgery. Her professional accomplishments start with a Ph.D. thesis on “The correlation between the foetal status and the ultrasound features of foetal annexes” and include collaborations in writing and editing 19 medical books specialised in obstetrics, gynaecology, ultrasound, and author in over 100 scientific articles both in domestic and international papers, longterm active participations in national conferences, congresses and also international medical events and fellowships.