Vasa praevia is a very rare obstetric disease. It manifests as painless vaginal bleeding in the middle and late stages of pregnancy, which can be easily misdiagnosed as placenta previa or early placental abruption. If treatment is delayed, it may lead to fetal death. The danger of vasa praevia is that when the presenting part descends, it can directly compress the blood vessels, causing fetal distress, but what is more dangerous is that when the fetal membranes rupture naturally or artificially, the vasa praevia fixed to the fetal membranes by collagen fibers can also be damaged and cause bleeding. This kind of bleeding is purely fetal bleeding, which is harmless to the mother's health, but it is extremely dangerous to the fetus.