HCG is the clinical abbreviation of human chorionic gonadotropin, and the normal value of HCG in women around 40 days of pregnancy is around 10,000-100,000 IU/L, but there is no specific normal value, because its value changes every day, and the same pregnant woman may have different values on the same day of examination. HCG is a protective hormone secreted by trophoblast cells, which clinically reflects the activity of the embryo and can be used to determine whether the fetus is developing normally through dynamic testing. If the HCG level is significantly low, it may be due to fetal failure or ectopic pregnancy. The HCG value doubles every 48 hours during the growing fetus, therefore, it is recommended to have an ultrasound examination after 42 days of pregnancy to get a more accurate picture of the gestational sac, germ and heart tube movement.