EC Gynaecology

The incidence of multiple gestations has risen substantially with the increasing use of assisted reproductive technologies, contributing to a higher prevalence of complications inherent to monochorionic (MC) twin pregnancies. MC twins are uniquely susceptible to vascular disorders due to shared placental circulation, with twin reversed arterial perfusion (TRAP) sequence representing one of the most severe manifestations. TRAP occurs in approximately 2.5% of monozygotic twins and is characterized by reversed perfusion from the pump twin to an acardiac twin through large arterioarterial and venovenous anastomoses. Early diagnosis relies on first trimester ultrasound and Doppler confirmation of retrograde arterial flow. Prognostic factors include a high acardiac-to-pump size ratio, evidence of cardiac compromise, and rapid acardiac growth. Management ranges from expectant surveillance to minimally invasive fetal interventions. Although emerging data support earlier intervention in selected cases, optimal timing remains uncertain, and further high-quality evidence is needed. TRAP sequence continues to pose a major clinical challenge, reinforcing the importance of specialized monitoring in MC pregnancies.

 Keywords: Twin Reversed Arterial Perfusion (TRAP) Sequence; Monochorionic Pregnancy; MC Twins

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