The placenta forms around 12 to 14 weeks of pregnancy, but it is not possible to generalize due to the large differences between individual pregnant women. The placenta can be formed around 12 to 14 weeks of pregnancy, usually around the 10th week, the placenta gradually begins to form, but usually the function of the placenta is not well developed, the structure is not obvious, the shape of the placenta can be vaguely seen through the ultrasound examination in the hospital, or the placenta may not be visible. The placenta is composed of the fetal leaf-like chorionic villus and the maternal fundus metaphase, and is an important organ to maintain the growth and development of the fetus, with the functions of nutrient supply, gas exchange, metabolite discharge, and synthesis of trophoblasts, etc. It is recommended that pregnant women should have regular checkups at the hospital. It is recommended that pregnant women should go to the hospital for obstetric examination regularly and intervene in time if there is any abnormality in the state of the placenta.