Recently, a mother-to-be at 38 weeks of pregnancy had an emergency cesarean section due to vaginal bleeding, a sharp drop in fetal heart rate, and abnormal fetal heart monitoring, which ultimately failed to save the life of the fetus. The culprit for this was the sail-shaped placenta. The difference between a sail-shaped placenta and a normal placenta is that the umbilical cord is not attached to the placenta, but to the fetal membranes outside the placenta. In this case, the vessels of the umbilical cord are scattered into several branches that fan out and travel in a circular pattern. These branches end up at the edge of the placenta. These fan-shaped branches are distributed between the amniotic membrane and the chorionic villus, forming a membranous structure like the canvas of a sailboat, hence the name sail-like placenta. The risk is great because the vascular branches around the sail-shaped placenta lose the normal umbilical cord structure and lack the support of huatong glue (embryonic connective tissue), which makes it very easy for vascular rupture to occur. Especially when these vascular branches are located below the fetal previa, across or close to the internal cervical os, they are medically called vascular anterior. When the vessels are torn by pressure or rupture of the fetal membranes, the fetus may suffer from hypoxia or acute blood loss. Since the blood volume in a full-term fetus is about 250 ml, fetal hemorrhagic shock can occur if the blood loss exceeds 20% to 25% (i.e., 50 to 60 ml), and therefore the fetal mortality rate is extremely high. Diagnostic methods At present, the most commonly used and easy and reliable method to detect and diagnose sail placenta is color Doppler ultrasound technology. With the continuous development and wide application of ultrasound technology and the improvement of ultrasonographers’ knowledge of sail placenta, the detection rate of prenatal sail placenta increases year by year. It has been found that prenatal ultrasound with purposeful observation of the placental cord attachment site can improve the display rate of sail placenta, with a diagnostic accuracy of 91%. However, there are many factors that affect ultrasound as an effective examination, such as too large or too small a gestational week, too little amniotic fluid, placenta located on the posterior wall and interference of fetal position, which reduce the correct rate of examination. The best time to diagnose placenta praevia is before 28 weeks of gestation for singleton and 20 weeks of gestation for twins, with a 97.7% compliance rate. If no obvious signs of fetal hypoxia or maternal complications are found, cesarean section can be performed at an optional date after 37 weeks of pregnancy. If a pregnant woman is at risk of preterm labor, she should be hospitalized at 30 to 32 weeks of gestation for observation, and if abnormal fetal heart monitoring or fetal distress occurs, the pregnancy should be terminated by cesarean section in a timely manner. If the diagnosis is not confirmed before delivery and vaginal bleeding occurs in late pregnancy or during delivery with fetal heart changes, after excluding placenta praevia, placenta abruptio, redness, etc., high suspicion of sail placenta with ruptured anterior vessels is needed to identify the source of bleeding in time and take measures to end the delivery quickly at the same time. In fact, placenta praevia is not scary, as long as doctors and mothers-to-be communicate effectively in time to detect the signs of placenta praevia and prevent it before it happens, the risk can be reduced to a minimum!