gynecology and obstetrics
Vasa Previa
Introduction
In vasa previa, membranes that contain fetal blood vessels connecting the umbilical cord and placenta overlie or are within 2 cm of the internal cervical os. Diagnosis is by ultrasonography. Management is fetal surveillance and delivery at about 34 weeks, or earlier for bleeding or nonreassuring fetal status. The source of bleeding in vasa previa is fetal, thus blood loss can rapidly impair fetal status. Vasa previa can occur on its own (see figure Vasa previa ) or with placental abnormalities, such as a velamentous cord insertion. In velamentous cord insertion, vessels from the umbilical cord run through part of the chorionic membrane rather than directly into the placenta. Thus, the blood vessels are not protected by Wharton jelly within the cord, making fetal hemorrhage more likely to occur when the fetal membranes rupture. Prevalence is about 1/2500 to 5000 deliveries. Fetal mortality rate may approach 60% if vasa previa is not diagnosed before birth. 