At 37 weeks of gestation, placental maturity should be grade 2 to 3. The placenta is intermediate between the mother and the fetus and consists of the bottom meconium, lobulated chorionic villus and amnion. In addition to material exchange between the mother and fetus, the placenta also has barrier function, immune regulation, endocrine, and synthesis of various cytokines and enzymes and other bioactive substances, but the barrier function is limited. The placenta is divided into 4 levels from occurrence, development, growth, maturation and aging by hair, i.e. 0 to 3. The placenta before 28 weeks of pregnancy is level 0, the placenta from 28 to 36 weeks of pregnancy is level 1, and the placenta from 36 to 40 weeks of pregnancy is level 2-3, so the maturity of the placenta corresponding to 37 weeks of pregnancy should be level 2-3.