In early pregnancy, the doubling of HCG can reach 0.7 times per day, and the doubling state is normal between 0.7 and 1 times. After 10 weeks, the HCG concentration gradually decreases to the level of tens of thousands of U/L by about 12 weeks, and then remains relatively stable until the end of the pregnancy. During late pregnancy. Therefore, the HCG does not double throughout the pregnancy, and the doubling is mainly significant in the early stages. In addition to the doubling of HCG, it is also important to pay attention to the development of the embryo.