The normal value of HCG is 0-5mIU/mL, within this range indicates no pregnancy, above this range indicates pregnancy. The level of HCG doubles after pregnancy, so monitoring the level of HCG in the blood can reflect the activity of the embryo. However, the blood test alone is not enough, but a pelvic ultrasound is also needed for the following purposes: 1) to determine the normal position of the pregnancy in the uterine cavity and to exclude ectopic pregnancy; 2) to determine the development of the embryo in accordance with the number of days of menopause, both in terms of the appearance of the fetal bud and fetal heart at the normal point in time, and to prevent the occurrence of a vacuolated pregnancy. With the gradual growth of the fetus, the purpose of ultrasound examination: 1. to exclude fetal malformation. 2. to prevent fetal growth retardation.