There are more and more clinical patients with fetal arrest, for various and complex reasons, some of which are unknown, the following obstetrics experts list some common causes of fetal arrest: 1, endocrine disorders: embryo implantation and continued development depends on the coordination of the complex endocrine system with each other, any one of the links is out of order, can cause miscarriage. The early development of the embryo requires three important hormone levels, one is estrogen, one is progesterone, and one is human chorionic gonadotropin. If the mother does not have enough endogenous hormones to meet the needs of the embryo, it may cause embryonic arrest and miscarriage. The most common one is luteal insufficiency, which can cause delayed endometrial development and short luteal phase, thus affecting the implantation of fertilized eggs or early pregnancy 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, if the pregnant woman carries some kind of antibody herself, it may affect the development of the embryo. There are four general factors affecting antibodies: one is anti-sperm antibodies, which may resist sperm-egg union; the second is anti-endometrial antibodies, which may affect the development of the embryo and resist the development of the embryo; the third is anti-ovarian antibodies, which can affect the quality of the egg; the fourth is called anti-chorionic gonadotropin antibodies, which is an important hormone that is actually secreted seven days after sperm-egg union. The first of these is the anti-chromosomal hormone, but if you have this antibody, it will resist the secretion of the hormone and cause the embryo to stop. 3. Uterus abnormalities: The internal environment of 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. Miscarriage due to uterine defects accounts for about 10% to 15%. The common ones are: (a) congenital abnormalities of Mullerian ducts including unicornuate, bicornuate and bicornuate uterus resulting in narrow uterine cavity and restricted blood supply, and abnormal development of uterine arteries which can lead to asynchronous molting and abnormal implantation. (b) Uterine adhesions, mainly caused by uterine cavity trauma, infection or residual placental tissue followed by uterine cavity adhesions and fibrosis, which prevent normal meconium formation and placental implantation. (c) Pregnancy failure can also be caused by reduced blood supply due to uterine fibroids and endometriosis leading to ischemia and venous dilatation, asynchronous metaplasia, abnormal implantation, and hormonal changes caused by fibroids. (d) Congenital or injurious endocervical relaxation and due to intrauterine treatment with ethylene estradiol. (4) Chromosomal problems: Chromosomal abnormalities can also cause early miscarriage due to failure of embryonic development. Chromosomal abnormalities include quantitative and structural abnormalities. Quantitative abnormalities can be classified as aneuploidy and polyploidy. The most common abnormal karyotype is triploidy, others are haploidy (4SX) and tetraploidy due to abnormal oogenesis leading to 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 needed to prevent the birth of chromosomally affected children. Obstetricians suggest that for chromosomal abnormalities, there is a theoretical chance of delivering babies with normal karyotypes and carriers. Current research has shown that chromosomal abnormalities can occur during gamete formation and embryonic development when both partners are chromosomally normal. If a woman is older than 35 years old and her eggs are aging, she is prone to chromosomal non-separation, leading to chromosomal abnormalities; semen abnormalities, such as large-headed malformed sperm most of which are diploid, form polyploid embryos after fertilization leading to miscarriage. 5, reproductive tract infection: in addition to the above factors, infection caused by early pregnancy miscarriage has been more and more attention from scholars at home and abroad. Severe TORCH infection in early pregnancy can cause embryonic death or miscarriage, while milder infections can also cause embryonic malformation. Studies have shown that cytomegalovirus can cause premature abortion and intrauterine fetal death. After maternal infection, the pathogen can exercise the placental infection through the blood, causing damage to the chorionic membrane and capillary endothelium, destroying the placental barrier, and the pathogen enters the fetus leading to miscarriage, embryonic arrest and fetal malformation. 6, environmental factors: changes in the physiological state during pregnancy, so that the mother’s absorption, distribution and excretion of therapeutic drugs and various environmentally harmful substances have changed significantly. In the early stages of development, the embryo is extremely sensitive to the effects of therapeutic drugs and environmental factors, and various harmful factors can lead to damage and even loss of the embryo at this time. 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 embryo development. Obstetricians suggest that early miscarriage has caused trauma to many women and families, in order to avoid such tragedies, the causes of fetal abortion need to be popularized as early as possible, to protect the smooth birth of the baby, starting from the source.