EP14.17: Outcome in diamniotic twin pregnancies with intertwin membrane cord insertion

Intertwin membrane cord insertion (IMCI), which refers to velamentous cord insertion into the dividing membrane, is rare situation in diamniotic twin pregnancies, while the detail of cases with the situation has not been fully documented. This case series aimed to clarify the delivery outcomes in cases of IMCI. The umbilical cord attachment site is verified through transabdominal ultrasonography during the second trimester of pregnancy. The delivery mode in cases with IMCI is determined on a case-by-case basis. We included cases with IMCI identified through ultrasonography among diamniotic twins delivered at our hospital from January 2016 to August 2022. Clinical information regarding the pregnancy and delivery outcomes was collected through a review of medical records. Out of 694 diamniotic twins delivered during the study period (324 monochorionic and 370 dichorionic), 10 cases (1.4%) including 1(0.3%) monochorionic and 9(2.4%) dichorionic, exhibited IMCI, all of which were confirmed post-delivery. No cases showed IMCI became apparent only after the delivery. Among these, 6 cases had IMCI in the first twins, whereas 4 had IMCI in the second twins. Three twins with IMCI involved fetal growth restriction, without any signs of fetal dysfunction noted before or during delivery. One case underwent elective Caesarean section due to IMCI considering the possibility of the development of vasa previa in the second twin after delivery of the first twin. Five cases underwent elective Caesarean section just for obstetrical indications other than IMCI, while 4 attempted trial of labour and eventually resulted in vaginal delivery. No instances of umbilical cord disruption were observed during delivery. The incidence of IMCI in diamniotic twin pregnancies may be rare. Just for our 10 cases' experiences, management based on prenatal diagnosis of IMCI did not lead to serious adverse outcomes related to IMCS in twins.