Embryonic arrest is a pathological pregnancy in which the early or middle stage embryo dies and all or part of the tissue remains in the official cavity and fails to be expelled naturally due to defects in the fertilized egg or the presence of factors unfavorable to the pregnancy in the mother’s body. It has been reported that embryonic sterilizations account for 10% to 18% of early pregnancies, and in recent years there has been a trend of gradual increase in the number of pregnancies ending in recurrent miscarriages. The causes of embryonic sterilizations are very complicated, including abnormal development of the pregnant egg or embryo caused by genetic factors, infectious factors, immune abnormalities, maternal endocrine disorders, uterine factors, systemic diseases, surgical trauma, etc. In addition, there are still about 40%-50% of the causes of embryonic sterilizations that are not yet known. Genetic factors include chromosomal abnormality of both parents or one of them and chromosomal test abnormality of embryo, chromosome number and structure abnormality, gene mutation, gene polymorphism, etc. The detection rate of chromosomal abnormality in the chorionic villi of spontaneous abortion is as high as 55%～66%. Immunologic factors It has been reported that 40% to 60% of embryonic sterilizations are related to immunologic factors. The implantation of a fertilized egg in the uterine cavity of the mother can be considered a semi-homologous transplantation phenomenon. When pregnancy occurs, immune cells produce immune tolerance at the maternal-fetal interface through a complex immune-regulatory mechanism that maintains the microenvironment necessary for embryo development and keeps the embryo from being rejected through immune-regulatory effects. The major immunoreactive cells in the uterine decidua are abundant natural killer (NK) cells, T cells and macrophages. Successful placental implantation depends on the correct balance of NK cell responses to trophoblast inhibition or activation. Infectious factors Common pathogens include Chlamydia (CT), Mycoplasma (UU), Toxoplasma gondii (TOX), cytomegalovirus (HCMV), and Gardnerella infection. The uterine cavity is invaded by Gardnerella vaginalis infection, which will cause inflammation of the official cavity, destroying the structure of amniotic membrane and chorionic villus, and decreasing its tissue function, and its endotoxin can induce a variety of cytokines to be released, which have a certain toxicity to the endometrium, impairing the growth of gestational tissues, and leading to the stagnation of embryonic development. Endocrine factors Luteal function defects, polycystic ovary syndrome, endometriosis, hyperprolactinemia, thyroid dysfunction, uncontrolled diabetes mellitus. During menstruation, the endometrial estrogen and progesterone receptor, apoptosis bcl-2 gene family and its regulator bax protein expression is disturbed, which destroys the local microenvironment of the endometrium for the preparation of implantation, thus resulting in infertility or miscarriage; patients with polycystic ovary syndrome due to the prolonged absence of ovulation, estrogen and progesterone secretion is uncoordinated, so that the endometrium during the implantation period and the planting of the endometrium and planting-related gene expression is weakened, thereby affecting embryo This affects several aspects of the embryo implantation process. Recent studies have found that elevated thyroid stimulating hormone in early pregnancy can lead to an increased risk of spontaneous abortion; in addition, progesterone, as a steroid hormone, plays a central role in the establishment and maintenance of pregnancy. Cell proliferation and apoptosis Apoptosis and proliferation in the placental villi and meconium are in a state of equilibrium during normal pregnancy. Excessive apoptosis is present in spontaneous abortion pregnancy tissues, and the occurrence of excessive apoptosis is associated with high expression of pro-apoptotic genes. When trophoblast invasiveness is inadequate, placental vascularization is poor, and the apoptosis “pro-apoptotic balance” is disrupted, pathological pregnancies may occur. Anatomical factors Uterine malformations (e.g., uterine hypoplasia, double uterus, unicornuate uterus, bicornuate uterus, uterine septum, etc.), uterine leiomyomas (e.g., submucosal leiomyomas and some interstitial leiomyomas), uterine adenomyomas, and adhesions in the cavity of the uterus can affect the development of embryo implantation and lead to miscarriage. Environmental and personal factors Electromagnetic radiation, atmospheric pollution, mental stress are all triggers of embryonic sterilizations. In addition, women’s personal bad habits such as alcoholism, smoking, drugs and coffee, etc.; menstrual history, pregnancy and childbirth history, oral contraceptives, pregnancy medication history, history of obstetrics and gynecological diseases, surgical trauma and chronic diseases, intrauterine infections, history of high fever in early pregnancy, history of X-ray exposure during pregnancy and early pregnancy, mental frustration, anxiety, and a lack of knowledge of reproduction may increase the risk of embryonic sterilizations.