Often patients and friends have gone through a lot of trouble, traveling to and from the hospital for months or even years, exhausting the experience and funds, carefully waiting for the moment of “lottery (pregnancy test)”, heard the doctor told the information that won the lottery, the joy is overflowing, but the second and third time… …When reviewing again, there are always some friends who can’t accept the news of failure and repeatedly ask the doctor why! Here, I would like to say a few words briefly. In fact, there are two kinds of failures: biochemical pregnancy and miscarriage. The mechanism of biochemical pregnancy is still unclear, and may be related to the embryo, endothelium, immune regulation, ovulation promotion program and other factors. According to foreign studies (Dickey’s study suggests that endometrial thickness <0.9cm has a higher chance of biochemical pregnancy), it is believed that most biochemical pregnancies may be due to endometrial factors, which may originate from a decrease in endometrial tolerance due to anatomical, immune or other reasons. Miscarriages, on the other hand, are mainly due to genetic defects of the embryo, in addition to endocrine abnormalities, autoimmune factors, and infectious factors, whereas the loss of mid-term pregnancies is most often due to abnormalities of the reproductive tract, such as cervical laxity and other factors.