Analysis of the ultrasonographic findings predictive of vasa previa

Objectives: To clarify the ultrasonographic findings indicative of prenatal vasa previa. Methods: The variables associated with placental and umbilical cord abnormalities were retrospectively analysed in cases with and without vasa previa. Results: Consecutive subjects were divided into those with vasa previa (10) and controls (4682). Abnormal placental forms and placenta previa/low-lying placenta were associated with vasa previa [odds ratio (OR) 21.9 and 28.0]. While the frequency of velamentous cord insertion was 1.6% in the controls, it was 90% in the cases with vasa previa (OR 552). In addition, low cord insertions in the uterus were observed in 90% of the patients with vasa previa and only in 0.4% of the controls (OR 2470). Descending cords were also frequently observed in patients with vasa previa (OR 89.8). Finally, a multivariable regression analysis demonstrated an OR of 65.1 (95% confidence interval (CI) 5.8-733) for velamentous cord insertion and an OR of 344.7 (95% CI 31-3838) for low cord insertion with regard to the risk of vasa previa. Conclusion: Our results suggest that confirmation of the placental cord insertion, including not only velamentous cord insertion but also the cords located on the lower uterine segment, is the best way to detect vasa previa.