Fetal abortion is a condition in which the development of the embryo stops in the early stages of pregnancy for one reason or another, and the ultrasound examination shows irregularities in the gestational sac or fetal morphology, absence of fetal heartbeat, and withering of the gestational sac. It is a clinical category of miscarriage or stillbirth. The main causes of fetal abortion are the following: 1. endocrine disorders: the embryo’s implantation and continued development depend on the coordination of the complex endocrine system, any one of which can lead to miscarriage. The early development of the embryo requires three important hormone levels, one is estrogen, one is progesterone, and one is human chorionic gonadotropin. As the mother, her own endogenous hormones are insufficient to meet the needs of the embryo, which may result in embryonic abortion and miscarriage. Luteal insufficiency can cause delayed endometrial development and short luteal phase, which can affect the implantation of fertilized eggs or early pregnancy miscarriage. Luteal insufficiency is often accompanied by other glandular function abnormalities, such as hyper- or hypothyroidism, diabetes, androgenism and hyperprolactinemia, etc. These factors are not conducive to embryonic development and are closely related to miscarriage. 2, immune factors: the embryo or fetus in the womb of pregnancy is actually a homozygous transfer, because the fetus is a combination of the genetic material of the parents and the mother can not be identical. The immune maladjustment between mother and fetus causes the mother to reject the fetus. Common autoimmune diseases are systemic lupus erythematosus, scleroderma, mixed connective tissue disease, dermatomyositis, etc. The second is the problem of reproductive immunity, which may affect the development of the embryo if we carry certain antibodies ourselves. The first one is anti-ovarian antibodies, which can affect the quality of the eggs. The second one is anti-sperm antibodies, which may resist sperm-egg union. The third is anti-endometrial antibodies, which may affect the development of the embryo if they are present. The fourth one is called anti-chorionic gonadotropin antibody, which is an important hormone that is secreted seven days after the sperm-egg union, but if you have this antibody, it will resist the secretion of the hormone and may cause the embryo to stop. 3, reproductive tract infection: in addition to the above factors, infection-induced early pregnancy miscarriage is increasingly being paid attention to by scholars at home and abroad. Severe TDRCH infection in early pregnancy can cause embryonic death or miscarriage. After maternal infection, the pathogen can exercise placental infection through the blood, causing damage to the chorionic villi and capillary endothelium, destroying the placental barrier, and the pathogen enters the fetus leading to miscarriage, embryonic arrest and fetal malformation. In recent years, many studies have shown that mycoplasma infection is associated with embryonic arrest, and the positive rate of cervical secretion mycoplasma infection in women with embryonic arrest is significantly higher than that in normal women, and there is a highly significant difference. 4. Uterus abnormalities: The internal environment in the uterus and the overall environment of the uterus may have an impact on the embryo. The internal environment is the endometrium, if it is too thin or too thick, it will affect the implantation. Miscarriages due to uterine defects account for about 10-15% of all miscarriages, and are commonly caused by: (1) congenital or injury-related relaxation of the endocervix and abnormal development of the cervix due to intrauterine treatment with ethylene estradiol, often leading to miscarriage in mid-term pregnancies. (2) Uterine adhesions, mainly caused by uterine trauma, infection, or residual placental tissue that causes adhesions and fibrosis in the uterine cavity. This prevents normal molting and placental implantation. (3) Pregnancy failure can also be caused by reduced blood supply due to fibroids and endometriosis leading to ischemia and venous dilatation, asynchronous molting, abnormal implantation and hormonal changes caused by fibroids. (4) Congenital abnormalities of the Mullerian ducts include unicornuate, bicornuate and bicornuate uterus resulting in a narrow cavity and restricted blood supply. Abnormal development of uterine arteries can lead to asynchronous molting and abnormal implantation. Environmental factors: Changes in the physiological state during pregnancy, the absorption, distribution and excretion of harmful substances in the mother’s body to therapeutic drugs and various environmental substances have changed significantly. Many drugs and environmental factors are important factors in causing early embryonic death or fetal malformations. Environmental hormones can act directly on the central neuroendocrine regulatory system, causing disruption of reproductive hormone secretion, decreased fertility and abnormal embryonic development. There are various environmental factors that cause miscarriage, including physical factors such as X-rays, microwaves, noise, ultrasound, high temperature, and heavy metals such as aluminum, lead, mercury, and zinc that affect the fertilized egg’s implantation or directly damage the embryo and cause miscarriage. Various chemical drugs such as dichlorohydrin, carbon disulfide, anesthetic gases, oral antidiabetic drugs, etc. can interfere with and impair reproductive function, causing embryo miscarriage, stillbirth, malformation, developmental delay and dysfunction. The problem is that the embryonic development is affected by bad habits such as smoking, alcoholism, coffee, drugs and certain medicines. 6, chromosomal problems: if chromosomal abnormalities can also cause the embryo not to develop and cause early miscarriage. Chromosomal abnormalities include quantitative and structural abnormalities, quantitative abnormalities can be divided into aneuploidy and polyploidy, the most common abnormal karyotype is triploidy, and trisomy 16 accounts for 1/3, which is often lethal. 25-67% of trisomy 21, 4-50% of trisomy 13, and 6-33% of trisomy 18 are bound to abort. Others are haploid, tetraploid due to abnormal oogenesis resulting in embryonic failure. Structural abnormalities include deletions, balanced translocations, inversions, and overlaps. Balanced translocations are the most common chromosomal abnormalities. Current research on chromosomal problems suggests that chromosomes pair, interchange and separate to form gametes, and gametes combine to form conjoined gametes. If there is an abnormality in one of the congeners, it results in failure to develop normally and can lead to miscarriage, stillbirth, stillbirth, and malformed children; therefore, prenatal diagnosis is required to prevent the birth of chromosomally affected children. There is no effective treatment for miscarriage and fetal abortion caused by carrying chromosomal abnormalities in Western medicine, and only prenatal genetic counseling and diagnosis can be performed. For chromosomal abnormalities, theoretically there is a chance of delivering normal karyotype and carrier babies, and prenatal diagnosis is done for these couples to ensure the birth of normal babies. Of course, current research has also shown that both couples have normal chromosomes, but chromosomal abnormalities occur during gamete formation and embryo development. For example, women older than 35 years old with aging eggs are prone to chromosome non-separation, resulting in chromosomal abnormalities; abnormal semen, such as large-headed malformed sperm most of which are diploid, form polyploid embryos after fertilization leading to miscarriage. The influence of adverse environment such as toxic chemicals, radiation, high temperature, etc. can also cause chromosomal abnormalities in embryos. Therefore, the key to prevent chromosomal abnormalities that lead to fetal abortion is to regulate the health of both spouses so that the functions of the internal organs are normally coordinated, the yin and yang are balanced, the best pregnancy is selected, and the bad environment is kept away.