Antepartum Management of Vasa Previa
10/1/2011 - L. Chesney Thompson, MD
Editor: Martin E. Olsen, MD
The exact frequency of vasa previa is difficult to determine, but it probably occurs in 1 in 1,500 to 5,000 pregnancies. Vasa previa occurs as a result of placentation and cord development; it is related to either a velamentous cord insertion (type I) or succenturiate placental lobe formation (type II). In either case, vasa previa occurs when fetal vessels traverse the membranes, separate from the umbilical cord or placenta, and overlie the cervix before the presenting fetal parts. Fetal exsanguination may occur if the vessel ruptures spontaneously or during artificial rupture of membranes. Vasa previa can be successfully managed through appropriate diagnosis, preparation and readiness for surgery.
Diagnosis has been improved with grayscale ultrasonography and color Doppler. Screening for and establishing the diagnosis is important. Debate exists regarding whether screening should be performed routinely in all pregnancies. Certain conditions associated with vasa previa such as low lying placenta, multi-fetal gestation, IVF or presence of an accessory lobe of the placenta should raise suspicion and warrant further investigation. Many ultrasonographers routinely perform cervical views during routine obstetrical ultrasound examinations, which may help detect vasa previa. Identification of the placental cord insertion site is a routine part of an anatomy scan and can aid in the diagnosis.
Once the diagnosis is established, successful management includes pelvic rest, possible hospitalization, and preterm delivery. These tenets are consistent although experts may disagree on details. The ultimate goal is to avoid rupture of membranes and potential fetal exsanguination by planning for surgical delivery of the fetus as close to maturity as possible. While hospitalization does not guarantee a good outcome, it does improve the chance of intact fetal survival compared to vasa previa rupturing outside of a hospital. For this reason, experts have recommended hospitalization starting at 30 to 32 weeks until delivery. Timing of delivery needs to balance fetal well-being and pulmonary maturity against the risk of spontaneous labor or spontaneous rupture of membranes. In addition to risk of vasa previa rupture, there is also concern for cord compression and subsequent fetal compromise. Elective cesarean delivery around 35 weeks may be optimal, and some experts recommend a course of antenatal steroids.
The addition of amniocentesis for fetal lung maturity poses its own risks and does not appear to add value. Some cases of vasa previa due to a succenturiate lobe (type II) may be treated antenatally with laser ablation of the vessels, but this procedure may not be available in many locations.
Bronsteen R, Whitten A, Balasubramanian M, Lee W, Lorenz R, Redman M, Goncalves L, Seubert D, Bauer S, Comstock C. Vasa previa: clinical presentations, outcomes, and implications for management. Obstet Gynecol. 2013;122:352-7.
Swank ML, Garita TJ, Maurel K, Das A, Perlow JH, Combs CA, Fishman S, Vanderhoeven J, Nageotte M, Bush M, Lewis D, Obstetrix Collaborative Research Network. Vasa previa: diagnosis and management. Am J Obstet Gynecol. 2016; 215:223.e1-6.
Initial Approval: 10/1/2011, Revised: 11/1/2016
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