A report of dizygotic monochorionic twins complictated with twin-to-twin transfusion syndrome

Introduction: So far it is widely accepted that monochorionic twins are exclusively monozygotic and therefore of the same sex. Twin-to-twin transfusion Syndrome (TTTS) is a well known complication of monochorionic multiple gestations and occurs in about 10%. We describe a rare case of dizygotic monochorionic twins that underwent laser therapy for TTTS. CASE REPORT: This pregnancy was conceived after ICSI treatment. First trimester ultrasound showed a viable twin pregnancy with findings indicative of monochorionic diamniotic twinning. At 18 weeks, there was development of severe TTTS, which was treated initially with a single amniodrainage at the referring hospital. Due to the recurrence of TTTS the patient was referred to our centre for laser coagulation. Before the intervention, ultrasound examination confirmed TTTS stage 3. After clear visualisation of placental vascular anastomoses, fetoscopic laser coagulation was performed without complications. Delivery took place at 29 weeks at the referring hospital by cesarean section after occurrence of preterm labour and PPROM. The neonates were discordant for sex. Detailed examination by neonatologists including ultrasound and hormone studies, revealed normal external female and male genitalia, respectively. DNA analysis showed normal 46 XX and 46 XY karyotype. Pathological examination confirmed a monochorionic- diamniotic twin placenta. Conclusion: Although very rarely, TTTS may occur in dizygotic twin gestations. In vitro fertilization may have had an influence on placental fusion in this case.