Usually, the file is established at around 12 weeks of pregnancy. This is because after the placenta is formed at 12 weeks of pregnancy, the fetal development is relatively stable and the chance of miscarriage will be significantly reduced. The chance of miscarriage is higher before the 12th week of pregnancy, and the cost is relatively high because a comprehensive examination will be conducted after the filing, and if the miscarriage occurs after the filing, there will be certain financial loss and the pregnant woman will have certain psychological trauma. Most of them are done at the local health center or maternal and child health center. In some areas, the cost of filing is subsidized. The doctor will arrange the time of each check-up after the file is opened. 5-10 check-ups are needed during the whole pregnancy, and the number of check-ups should be increased if there are special circumstances. In addition, the more specific maternity tests during pregnancy include NT test around 12 weeks of pregnancy, Tang screening test between 16-21 weeks of pregnancy, 4D test between 22-28 weeks of pregnancy, and diabetes screening between 24-28 weeks of pregnancy.