Normally, the umbilical cord is attached to the placenta, near the center of the fetal surface. If the umbilical cord is attached to the fetal membranes, the vessels of the cord enter the placenta through the space between the amniotic membrane and the chorionic villi, which is called sail-like attachment of the umbilical cord. If the vessels on the fetal membranes cross the inner cervical opening and are located in front of the fetal previa, it is called an anterior vessel. Due to the lack of protection of the anterior vessels, they are easily compressed by contractions or broken during rupture of the membranes, resulting in obstruction of the blood circulation of the umbilical cord and fetal hypoxia due to blood loss, or even sudden death. If the diagnosis of umbilical cord sail attachment combined with anterior vascularity is made, the fetus should be closely monitored during pregnancy and elective cesarean section should be performed when the fetus is mature to reduce perinatal mortality.