Systematic screening for vasa previa at the 20-week anomaly scan.

Abstract

The presence of vasa previa carries a high risk for severe fetal morbidity and mortality due to fetal bleeding caused by injury to unprotected fetal vessels when rupture of membranes occurs. Previously, it has been shown that prenatal diagnosis significantly improves the outcome. However, systematic screening for vasa previa is not generally performed and clinical studies demonstrating the performance of systematic screening for vasa previa in routine clinical practice are rare. The objective of this study was to assess the performance of systematic screening for vasa previa by determining placental cord insertion at the 20-week anomaly scan. This is a retrospective study of 6038 pregnant women between 18+0 and 24+0 gestational weeks who were prospectively screened for vasa previa by depiction of the site of placental cord insertion at the 20-week anomaly scan. Pregnancies with marginal or velamentous cord insertion underwent vaginal sonography for examination for vasa previa. In cases with succenturiate or bilobed placentas, the bridging vessels were depicted, and vaginal sonography was performed if necessary. There were 21 cases of vasa previa and all were diagnosed prenatally. In 18 cases, the cord insertion was marginal or velamentous. The remaining three cases had placental anomalies, which necessitated a detailed examination. All pregnancies with vasa previa were delivered at a mean of 35.2 (SD 1.8) gestational weeks by cesarean section. Among pregnancies affected by vasa previa, all fetuses survived. The median birthweight was 2390g (range 1200-2990g) and the mean umbilical artery pH 7.34 (SD 0.04). The median 5-min APGAR score was nine (range 7-10). None of the fetuses or neonates died or required blood transfusions. In all pregnancies of the whole cohort which were complicated by fetal or neonatal demise and in neonates with a 5-min APGAR score ≤5 and/or an umbilical artery pH ≤7.10, fetal blood loss was excluded as a cause of the poor obstetric outcome. Screening for vasa previa is feasible and efficient, taking into account the site of placental cord insertion in pregnancies not affected by placenta previa and bilobed and succenturiate placenta.