The main reasons why the HCG of pregnancy has been low are as follows: i. Due to the poor quality of the embryo, it is not able to stimulate the ovarian corpus luteum to secrete sufficient amount of HCG. ii. The function of the female ovarian corpus luteum itself is not good, and it is not able to secrete sufficient amount of HCG. iii. It is related to individual differences, because the body does not respond obviously to the elevated hormone, if the HCG has been low, the embryo in the uterine cavity is well developed, there is the appearance of fetal buds and fetal heartbeat It can be observed temporarily. Fourth, if ectopic pregnancy occurs and the value has been low, low HCG should be ruled out, pay attention to rest and give appropriate HCG medication for supplementation to see if it can raise the level of HCG. If the embryo does not grow after 1-2 weeks of treatment, no fetal bud and fetal heartbeat appear, and vaginal bleeding gradually increases with lower abdominal pain, it means that embryonic abortion is spontaneous, and the pregnancy should be terminated in time.