The phenomenon that the blood HCG value drops and then rises during pregnancy may be due to testing errors or other reasons, mainly due to the following situations: 1. If a pregnant woman has a decrease in HCG, intramuscular injection of chorionic gonadotropin can restore the decreasing blood HCG level to normal, so that the pregnancy can continue, this can happen mainly due to the effect of drugs; 3. It is also necessary to exclude the possibility of choriocarcinoma, which should be taken seriously and further monitoring of blood HCG is recommended to take treatment measures under the guidance of doctors.