There are 4 grades of placental maturity: 0, 1, 2, and 3. Grade 2 indicates a mature placenta. Placental maturity grading is generally determined by ultrasound, which is based on a combination of the chorionic villi, parenchyma and basal layer of the placenta. grade 0 refers to an immature placenta, which is usually before 28 weeks of gestation. grade 1 means that the placenta is basically mature, which is mostly seen between 29 and 36 weeks of gestation. grade 2 means that the placenta is mature, which is mostly seen after 36 weeks. grade 3 means that the placenta is mature and tends to age, and placental function begins to decline, which may affect the normal transport of oxygen and nutrients. Grade 3 indicates that the placenta has matured and is aging, and the function of the placenta is beginning to decline, which may interfere with the normal transportation of oxygen and nutrients, and may pose a certain risk to the fetus, and is most common after 38 weeks of gestation. Pregnant women with high blood pressure or diabetes during pregnancy, the placenta will mature or even age prematurely, and timely medication is needed to improve placental function.