Placental maturity grade 1 usually occurs in late gestation (30-32 weeks), and the ultrasound shows a lightly undulating bright line on the placental villi plate, slightly coarse placental parenchyma, slightly strong echogenicity, and still no basal lamina, indicating basic placental maturity. The placental maturity is one of the markers to measure the normal development of the fetus and is divided into four grades: grade 0, grade 1, grade 2 and grade 3. grade 0 indicates that the placenta is not mature; grade 1 indicates that the placenta is basically mature; grade 2 indicates that the placenta is mature; grade 3 indicates that the placenta is senile. In the middle of pregnancy (13-28 weeks), placenta maturity is grade 0; in the late pregnancy (30-32 weeks), placenta maturity is grade 1; after 36 weeks, placenta maturity is grade 2; after 38 weeks, placenta maturity enters grade 3, marking complete maturity of the placenta.