Vasa previa is a condition where fetal blood vessels run across the internal opening of the uterus. These vessels are at risk for rupture when the supporting membranes rupture as they often due during labor or before the start of labor. If this happens, a fetus could exsanguinate in a matter of minutes.
At SDPC, we routinely screen patients for vasa previa with transvaginal ultrasound because the risk for fetal exsanguination can be averted by early cesarean delivery. Vasa previa is thought to occur in about 1 in every 2000 pregnancies. It is more common in multiple gestations and in IVF pregnancies. Vasa previa is seen more commonly associated with velamentous cord insertion, marginal cord insertion, and bilobed placentas.
- Cesarean section: The most important step is to schedule a C- section before the onset of labor, generally at 34-35 weeks.
- Ultrasound assessment: Vasa previa does not result in placental insufficiency, therefore, the developing baby should grow normally. However, associated conditions such as velamentous cord insertion or bilobed placentas may warrant serial growth measurements. The cervix should be assessed intermittently by trans-vaginal ultrasound. Under normal circumstances, this is done every 2 weeks from 24 weeks, and weekly from 32 weeks of gestation.
- Admission: We offer antenatal admission to all patients with Vasa Previa at 26 weeks and recommend hospitalization at 30-32 weeks, even in the absence of other obstetric risk factors. (Gagnon et al: Guidelines for the management of vasa previa. J Obstet Gynaecol Can. 2009 Aug;31(8):748-60.) Earlier admission may be recommended for the following circumstances: a history of preterm delivery; risk factors for preterm delivery, including reduced cervical length, relevant maternal co-morbidities; or remote home location.
- Steroids for fetal lung maturation: If patient has any indications for preterm admission, antenatal steroids are given, and a second repeat course is recommended if delivery is planned at or before 34 weeks.
- Serial nonstress tests. While not of proven benefit, serial nonstress test starting at 28-30 weeks gestation is recommended by the authors of the article in uptodate.com, and is a reasonable precaution in women who are managed by outpatients.