During pregnancy, the phenomenon of blood HCG values drop and rise, may be a detection error, may also be caused by other reasons, mainly in the following cases: 1, the laboratory results are not accurate, sometimes there can be errors, or various hospitals have differences in the detection method, manifested in the decline of blood HCG values rise, it is recommended that the review; 2, the drug factor, can be seen in the occurrence of preterm miscarriage during the treatment of abortion, such as pregnant women first appear HCG decline, intramuscular injection of chorionic gonadotropin, so that the decline in blood HCG levels back to normal, so that pregnancy can continue; this situation is mainly due to the role of drugs. Such as pregnant women first appear HCG decline, intramuscular chorionic gonadotropin injection, so that the decline in blood HCG levels back to normal, so that the pregnancy can continue, this situation is mainly due to the role of drugs can occur; 3, blood HCG values in early pregnancy decline and rise, may occur in ectopic pregnancies or embryonic arrest of development of the fertility preservation treatment; 4, after the clearance of the uterus surgery or abortion may also occur after the decline and rise of blood HCG, also recommended for review; 2, drug factors, can be seen in the occurrence of preterm miscarriage for fertility preservation treatment period. The possibility of choriocarcinoma should be ruled out. In this case, high attention should be paid and it is recommended to further monitor the blood HCG and take measures under the guidance of the doctor.