Failed IVF implantation or miscarriage or habitual miscarriage is a very bad thing for sisters. This is because it brings not only physical harm, but also psychological impact is deeper, farther and more terrible. The better the embryo grade is, the higher the rate of implantation is, and the causes of miscarriage and embryonic abortion can be divided into three aspects: embryonic, maternal and paternal, among which embryonic causes are the most important. Embryonic chromosomal abnormalities and genetic abnormalities account for 60% to 70% of embryonic abortions, which are broken down in detail below. 1. Chromosomal problems If chromosomal abnormalities are present, they can also lead to early miscarriage due to non-development of the embryo. 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, 4-150% of trisomy 13, and 6-33% of trisomy 18 are bound to miscarriage. Others are haploid (4SX) and tetraploid due to abnormal oogenesis resulting in embryonic failure. Structural abnormalities include deletions, balanced translocations, inversions, overlaps, and other closures. Balanced translocations are the most common chromosomal abnormality. Aging eggs are the number one killer of older sisters, and chromosomal variants that occur due to aging – appear to be more common in women over the age of 35. After the age of 40, the tendency for this variation is even stronger reaching almost 85% variation. Screening: In cases of miscarriage or abortion, chromosomal variants in the embryo are suspected, but the genetic chromosomes of both spouses are normal, mainly due to aging of the eggs. In general, eggs with chromosomal variants do not develop into embryos after fertilization, or do not reach the fifth or sixth day. However, there are some sisters who have biochemical or fetal arrest/miscarriage, depending on how far the abnormal embryo has traveled. The older male partner may also have a sperm chromosome variation that causes the female partner to miscarry, but I think the main reason is the aging of the female eggs. Generally women older than 35 years old have aging eggs and are prone to chromosomal non-separation, leading to 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. 2. Endocrine disorders Embryo implantation and continued development depend on the coordination of the complex endocrine system with each other. During the early development of the embryo, three important hormone levels are needed, one is estrogen, one is progesterone and one is human chorionic gonadotropin. As the mother, her own endogenous hormones are not sufficient to meet the needs of the embryo, which may cause 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. Immunological 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 cannot 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 we carry certain antibodies ourselves, it may affect the development of the embryo. In fact, the detection of antibodies is not the same in every hospital, and the doctors’ opinions are not the same. From the perspective of our research, we believe that there are four factors that affect the development of the embryo. The fourth is called anti-chorionic gonadotropin antibody, which is an important hormone that is actually secreted seven days after the union of sperm and egg, but if you have this antibody, it will resist the secretion of the hormone and may cause the embryo to stop. 4. 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. Miscarriages due to uterine defects account for about 10% to 15% of miscarriages, and the common ones are (1) congenital abnormalities of the Mullerian ducts including unicornuate, bicornuate and bicornuate uterus resulting in a narrow uterine cavity and restricted blood supply. Abnormal development of the uterine arteries can lead to asynchronous metaplasia and abnormal implantation. (2) Uterine adhesions, mainly caused by uterine cavity trauma, infection or residual placental tissue followed by uterine cavity adhesions and fibrosis. This hinders normal molting and placental implantation. (3) Pregnancy failure can also be caused by reduced blood supply due to fibroids and endometriosis resulting in ischemia and venous dilatation, asynchronous molting, abnormal implantation and hormonal changes caused by fibroids. (4) Congenital or injurious endocervical laxity and abnormal cervical development due to intrauterine treatment with ethylene estradiol often lead to miscarriage in midterm pregnancies. (5) Reproductive tract infection: In addition to the above factors, early pregnancy miscarriage due to infection is receiving more and more attention from scholars both at home and abroad. Severe TDRCH infections in early pregnancy can cause embryonic death or miscarriage, while milder infections can also cause embryonic malformations. Studies have shown that cytomegalovirus can cause premature miscarriage and intrauterine fetal death. After maternal infection, the pathogens can travel through the bloodstream to infect the placenta, causing damage to the endothelium of the chorionic villi and capillaries, and destroying the placental barrier, resulting in 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. (6) Environmental factors: Changes in the physiological state during pregnancy cause large changes in the absorption, distribution and excretion of therapeutic drugs and various environmentally harmful substances in the mother’s body, and in the early stages of development, the embryo is extremely sensitive to the effects of therapeutic drugs and environmental factors, at which time various harmful factors can lead to embryonic damage and even loss. Many drugs and environmental factors are important factors in causing early embryonic death or fetal malformation. Environmental hormones can act directly on the central neuroendocrine regulatory system, causing disruptions in 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 functional disorders. The early embryonic development can be affected by bad habits such as smoking, alcohol, coffee, drugs, and certain medications.