Prenatal sonographic diagnosis of pseudomonoamniotic twins: Two-case series

Pseudomonoamniotic twins (PMA), a rare and high-risk complication of diamniotic twins, result from the rupture of the dividing membrane. This condition is associated with fetal malformations and demise. Current prenatal ultrasound detection rates remain suboptimal, with most cases diagnosed only after umbilical cord entanglement or intrauterine fetal death.Here, we present 2 cases of PMA diagnosed prenatally via ultrasound and focus on discussing their sonographic features.

Case 1: No first-trimester ultrasound was performed in this case. The patient visited our hospital for the first ultrasound examination at 12weeks' gestation.Case 2: Follow-up ultrasound was performed 1 day after amniocentesis at 26 weeks' gestation.

Case 1: PMA with amniotic band syndrome.Case 2: PMA with cord entanglement and fetal distress.

Case 1: The twins did not receive any specific treatment.Case 2: Emergency cesarean delivery was performed.

Case 1: Induction of labor at 13 weeks' gestation.Case 2: Preterm twins admitted to neonatal intensive care unit, discharged after 50 days with favorable outcomes.

Targeted evaluation of the dividing membrane at the umbilical cord insertion sites may improve the detection of spontaneous PMA. Sonographic manifestations of dividing-membrane rupture include the multilayer folding sign, absence of the dividing membrane, 1 fetus entering the amniotic sac of the co-twin, and umbilical cord entanglement. The multilayer folding sign may be an early indicator of the rupture dividing membrane. Complications resulting from dividing-membrane rupture warrant heightened vigilance, especially amniotic band syndrome and cord entanglement, both of which are associated with adverse perinatal outcomes.