Doubling of hcg is generally said to be approximate, and clinically it does not necessarily mean that the HCG on the second day is twice as high as the first day; at 6-8 weeks of gestation, hcg increases at a rate of 66% daily. Early in a woman’s pregnancy, if the gestational sac is well developed, HCG may show a doubling-like increase. However, this doubling is only an approximation. If HCG is found to be 500 mIU/mL on the first day, it does not mean that it will be 1000 mIU/mL on the next day. Sometimes this increase may not reach the level of doubling, but it does not mean that there is a problem with the development of the embryo. However, if the growth rate is <66% in 48 hours, the prognosis of the pregnancy is poor. Checking the HCG value in early pregnancy can assess the development of the embryo. If the HCG value is significantly lower than the corresponding gestational week, and the rate of increase is slow, there may be abnormal embryonic development or ectopic pregnancy. Pregnant women need to further check ultrasound, progesterone, etc. under the guidance of the doctor, and at the same time, according to the clinical symptoms of a comprehensive assessment.