Abstract Vasa previa (VP) is a dangerous obstetric condition associated with perinatal mortality and morbidity. In vitro fertilization (IVF) is a risk factor for VP due to the high incidence of abnormal placentation. The diagnosis should be made prenatally, because fetal mortality can be extremely high. We report two cases to demonstrate the accuracy of transvaginal ultrasound in the prenatal diagnosis of VP. A...