Velamentous cord insertion in monochorionic twin gestation. An added risk factor.

OBJECTIVE: To study the effects of umbilical cord insertion combinations on outcomes in monochorionic (MC) twin placentas. STUDY DESIGN: Sixty consecutive MC placentas were analyzed by cord insertion patterns with regard to growth discordance, placental parenchymal sharing, types and patterns of intertwin vascular anastomoses, perinatal mortality and frequency of fetofetal transfusion. Cord insertions were classified as central/eccentric (CEN) or velamentous/ marginal (VEL). RESULTS: Forty-five percent of the twins had VEL insertions. The CEN/VEL combination was found in 53% of pairs. The CEN/VEL group had the highest rates of growth discordance > 20%, unequal placental parenchymal sharing, uncompensated anastomoses and perinatal demise. CONCLUSION: VEL cord insertion and the CEN/VEL combination are indicators of high-risk subgroups within MC twins. VEL cord insertions can be diagnosed by ultrasound, identifying these high-risk groups.