Abnormal insertion of umbilical cord Vasa previa 2021-08-18T12:29:15Z Vasa previa occurs when the membranes that contain the umbilical cord traverse the membranes overlying the internal os of the cervix. There is a high risk of fetal mortality if not identified perinatally. This abnormality is problematic because of the location of the unprotected vessels. If the fetal head compresses these vessels, it can result in fetal hypoperfusion and acidemia. If the vessels rupture it can lead to fetal hemorrhage.