The doubling of HCG in patients with hyperemesis gravidarum has a significantly faster rate of increase relative to the change in HCG in a normal pregnancy. For example, in a normal pregnancy, HCG, or human chorionic gonadotropin, in the body should increase by about 60% over a 24-hour period and can double at 48-hour intervals. However, in the case of hyperemesis gravidarum, because of the marked acceleration of intrauterine trophoblast differentiation, it is easy to see a marked increase in the rate of doubling of HCG, and even a doubling can be achieved in a 24-hour period. However, the presence of hyperemesis gravidarum can only be suspected by the abnormal changes in HCG alone, but the diagnosis of hyperemesis gravidarum cannot be confirmed by the changes in HCG. When there is an abnormal and rapid change in HCG, it is necessary to perform an examination of the gestational sac by ultrasound more than 35 days after the last menstrual period to observe whether the gestational sac has a normal morphology, and then confirm the diagnosis of gravidarium and exclude the risk.