Supplementary Material for: Intertwin Membrane Placental Cord Insertions in a Dichorionic Diamniotic Twin Pregnancy: Case Report

Introduction: Intertwin membrane cord insertion (IMCI) is a rare variation of velamentous cord insertion (VCI) that can be seen in dichorionic twin pregnancies. This condition exposes fetal vessels to risks such as compression and rupture, which can lead to complications including fetal growth restriction (FGR) and preterm delivery.

Clinical Presentation: A 30-year-old woman, gravida 1 para 0, was referred at 19+5 weeks for evaluation of a dichorionic diamniotic twin pregnancy due to an abdominal cyst in Twin A, transposition of the great arteries in Twin B, and suspected abnormal cord insertions.

Diagnosis & Management: Ultrasound evaluation confirmed IMCI, with both umbilical cords inserting into the intertwin membrane before reaching the placenta. MRI corroborated the findings. Doppler studies remained normal until 34+2 weeks, when signs of severe FGR and abnormal umbilical artery Dopplers prompted delivery by cesarean section. The twins were delivered preterm, and postnatal evaluation confirmed VCI.

Conclusion: This case highlights the importance of early identification of IMCI, as it necessitates close monitoring and timely intervention to optimize perinatal outcomes.