A case of vasa previa diagnosed prenatally, and review of the literature.

The perinatal mortality rate of vasa previa is high if it is not prenatally diagnosed. In this report, a case of vasa previa diagnosed prenatally is presented. Antepartum hemorrhage at 24 weeks of gestation prompted a close investigation of the uterine cervix, internal os, and placenta. We detected a low-lying bilobed placenta with umbilical cord insertion in the lower uterine segment. Furthermore, one of the connecting vessels of the bilobed placenta passed directly above the internal os. Vasa previa was suspected and confirmed with color Doppler and MRI. The fetus was delivered uneventfully by planned Cesarean section at 38 weeks of gestation. It should be considered that placenta previa (including low-lying placenta), bilobed placenta, and umbilical cord insertion in the lower uterine segment are associated with high risk of vasa previa. Ultrasound screening for cord insertion and placenta around the internal os enables efficient and certain detection of vasa previa.