Vasa previa is not infrequent.

OBJECTIVE: To clarify certain frequency of vasa previa using ultrasonography.

METHODS: Umbilical cord insertion site were examined prospectively by the ultrasound during first trimester in 3647 cases between 2006 and 2011.

RESULTS: 10 cases (1: 365) of vasa previa were found. All cases with vasa previa at the delivery had been diagnosed as a lower cord insertion in the uterine cavity in the first trimester, whereas we do not have any misdiagnosed cases.

CONCLUSION: Although it is believed that the incidence of vasa previa is very rare, according to our ultrasonographic evaluation vasa previa is not infrequent. Additional systematic identification of umbilical cord abnormalities from early gestation is recommended.