Placenta grade 1 at 20 weeks gestation is an abnormality. The whole process of placenta from occurrence, development, growth, maturity to aging can be divided into four grades. One of them is grade 0 before 28 weeks of pregnancy, grade I from 28 to 36, and grade II-III from 36 to 40 weeks, so according to normal, 20 weeks of pregnancy should be grade 0. And the placenta grows to grade 1 at 20 weeks of pregnancy, which is a developmental phenomenon relative to 28 to 36 weeks, indicating that the placenta grows and develops relatively fast. It is important to pay attention to the active detection of the umbilical artery blood flow and other conditions, once there is an abnormality, it is considered to be the existence of intrauterine hypoxia in the fetus, and it is necessary to pay attention to timely hospital consultation. Therefore, the phenomenon of placenta 1 at 20 weeks of pregnancy, you can go to the hospital to improve the examination to clarify the specific cause of the disease, and under the guidance of the doctor for treatment.