The exact cause of sail-shaped placenta is not clear, but it is considered to be related to the low position of the placenta in the early stage and chorionic villous malnutrition at the umbilical cord attachment. Sail-like placenta refers to the abnormal attachment of the umbilical cord to the fetal membranes, which resembles a sailboat, hence its name. The exact cause of the formation of sail-like placenta is not clear, but it may be related to the low position of the placenta in early stages, or it may be due to chorionic villous malnutrition at the umbilical cord attachment site, and so on. In addition, twins, multiple pregnancies, placenta praevia, paracentesis, etc., are also prone to sail-shaped placenta. Sail-like placenta has a great impact on the fetus, and may easily lead to fetal growth restriction, intrauterine oxygen deficiency and other risks.