The abortion of a biochemical pregnancy occurs in the early stages of pregnancy, when the sperm and egg are transported to the uterus after union, but do not successfully implant or stop developing before the pregnancy can be detected on ultrasonography, and are aborted with menstruation, accounting for about 2/3 of early abortions. It is not clear about the etiology of biochemical pregnancy, but it has been found that biochemical pregnancy is related to maternal factors and embryonic and male factors, and the thickness and tolerance of the endometrium, the quality of the egg and the quality of the embryo are closely related to the occurrence of biochemical pregnancy. The following are the details: 1. Endometrial thickness: Patients with endometrial thickness <9mm have a higher probability of biochemical pregnancy. 2, maternal hormone levels: various hormones in the mother have an impact on the various processes of ovulation, fertilization and implantation, such as estradiol and luteinizing hormone levels are abnormal, there is a possibility of biochemical pregnancy. 3, poor egg quality: the quality of eggs directly affects the quality of embryos, which is associated with the occurrence of biochemical pregnancy. 4, embryonic chromosomes: embryonic chromosomes have an impact on the quality of the embryo, and to some extent can cause biochemical pregnancy. 5, other: biochemical pregnancy is also related to the patient's age, previous history of biochemical pregnancy or miscarriage, maternal immune factors, male age and semen quality, etc. In conclusion, there are many factors that cause biochemical pregnancy, but biochemical pregnancy is usually the result of the superiority of the embryo, which does not affect the pregnant woman and does not affect the next pregnancy, only pregnant women with repeated biochemical pregnancy need special attention.