What are the main causes of fetal pause? There are six main reasons, which are briefly described as follows:
First, endocrine disorders
The implantation and continued development of the embryo depend on the complex endocrine system coordinating with each other. Any abnormality in a link can lead to a miscarriage. During the early development of the embryo, three important hormone levels are needed: estrogen, progesterone, and human chorionic gonadotropin. As for the mother, if her endogenous hormones are insufficient, she cannot meet the needs of the embryo, which may cause the embryo to stop developing and result in a miscarriage. The most common is the dysfunction of the corpus luteum, which can cause delayed development of the endometrium and a short luteal phase, thus affecting the implantation of the fertilized egg or leading to early pregnancy miscarriage. Those with incomplete corpus luteum function often have other glandular dysfunction, such as hyperthyroidism or hypothyroidism, diabetes, relative increase of androgenism, and hyperprolactinemia, etc. These factors are all unfavorable for embryo development and are closely related to miscarriage.
Second, immune factors
The embryo or fetus in the uterine cavity during pregnancy is actually a xenotransplantation of the same species, because the fetus is a combination of the genetic material of the parents, and it cannot be completely the same as the mother. The immune incompatibility between the mother and the fetus can lead to rejection of the fetus by the mother. Common autoimmune diseases include systemic lupus erythematosus, scleroderma, mixed connective tissue disease, dermatomyositis, and others. The second is the problem of reproductive immunity. If we carry a certain antibody ourselves, it may affect the development of the embryo. In fact, the detection of antibodies varies from hospital to hospital, and the opinions of doctors are also different. From our research perspective, we believe that there are four influencing factors: first, anti-sperm antibodies, if present, may resist the combination of sperm and egg; second, anti-endometrial antibodies, if they exist, may affect the development of the embryo, and resist the development of the embryo; third, anti-ovarian antibodies, if present, may affect the quality of the egg; fourth, anti-corpus luteum gonadotropin antibodies, this hormone is an important hormone that needs to be secreted seven days after the sperm and egg combine. However, if there is such an antibody, it may resist the secretion of the hormone, which may cause the embryo to stop developing.
Three, uterine abnormalities
Both the internal environment of the uterus and the overall environment of the uterus can affect the embryo. The internal environment is the endometrium, if it is too thin or too thick, it will affect implantation. Abortion caused by uterine defects accounts for about 10% to 15%, common ones include:
1, congenital abnormalities of the Müllerian duct, including unicorne uterus, bicornate uterus, septate uterus, and bicorne uterus, leading to a narrow uterine cavity and restricted blood supply. Abnormal development of uterine arteries can lead to asynchronous decidualization and abnormal implantation.
2, intrauterine adhesion, mainly caused by intrauterine trauma, infection, or placental tissue residue, leading to intrauterine adhesion and fibrosis. It hinders normal decidualization and placental implantation.
3, uterine fibroids and endometriosis cause reduced blood supply, leading to ischemia and venous dilation, asynchronous decidualization, abnormal implantation, and hormone changes caused by fibroids can also lead to pregnancy failure.
4, congenital or traumatic cervical internal os relaxation, as well as cervical development abnormalities caused by ethinyl estradiol treatment during fetal development, often lead to mid-trimester pregnancy loss.
Four, the issue of chromosomes
If there is a chromosomal abnormality, it can also lead to the failure of embryo development and early abortion. Chromosomal abnormalities include quantitative and structural abnormalities, of which quantitative abnormalities can be divided into aneuploidy and polyploidy. The most common abnormal karyotype is trisomy, with 16 trisomy accounting for 1/3, often being lethal. In 25% to 67% of trisomy 21, 4% to 50% of trisomy 13, and 6% to 33% of trisomy 18, there will be inevitable abortion. Other abnormalities include monosomy (4SX) and tetraploidy due to abnormal cleavage, leading to the failure of embryo development. Structural abnormalities include deletions, balanced translocations, inversions, and overlaps. Balanced translocation is the most common chromosomal abnormality. Current research on chromosomal issues believes that pairing, crossing over, and separation of chromosomes form gametes, and gamete combination forms zygotes. If there are any abnormalities in the zygotes, it will lead to abnormal development, which can cause abortion, stillbirth, neonatal death, and malformed infants. Therefore, prenatal diagnosis is necessary to prevent the birth of children with chromosomal abnormalities. For abortions and fetal stasis caused by chromosomal abnormality carriers, there is currently no effective treatment method in Western medicine, and only prenatal genetic counseling and diagnosis can be carried out. In theory, there is an opportunity for normal nuclear type and carrier infants for chromosomal abnormalities. For these couples, prenatal diagnosis should be done to ensure the birth of normal infants. Of course, current research also shows that both partners have normal chromosomes, but chromosomal abnormalities may occur during the formation of gametes and the development of the embryo. If the age of the female is greater than 35 years, the egg will age, and it is easy to have chromosomal non-separation, leading to chromosomal abnormalities; abnormal seminal fluid, such as the sperm with大头畸形, most of which are diploid, can form polyploid embryos after fertilization, leading to abortion. The influence of adverse environmental factors such as toxic chemicals, radiation, and high temperature can also cause chromosomal abnormalities in the embryo. Therefore, the key to preventing fetal stasis caused by chromosomal abnormalities is to adjust the physical condition of both partners, so that the functions of each organ are normal and coordinated, yin and yang are balanced, choose the best time for pregnancy, and stay away from adverse environments.
Five, reproductive tract infection
In addition to the above factors, early pregnancy loss caused by infection is increasingly attracting attention from Chinese and foreign scholars. Severe TDRCH infection in the early stage of pregnancy can cause embryonic death or abortion, and mild infection can also cause embryonic malformation. Studies have shown that cytomegalovirus can cause missed abortion and intrauterine fetal death. After the mother is infected, the pathogen can pass through the blood to infect the placenta, causing damage to the villous and capillary endothelium, destroying the placental barrier, and causing abortion, embryo stasis, and fetal malformation. In recent years, many studies have shown that mycoplasma infection is related to embryo stasis, and the positive rate of mycoplasma infection in cervical secretions of women with embryo stasis is significantly higher than that of normal women, with extremely significant differences.
Six, environmental factors
Changes in the physiological state during pregnancy cause significant changes in the absorption, distribution, and excretion of treatment drugs and various environmental harmful substances in the mother's body. In the early stage of development, the embryo is extremely sensitive to the effects of treatment drugs and environmental factors. At this time, various harmful factors can cause damage to the embryo, even loss. Many drugs and environmental factors are important factors in the death or malformation of early embryos. Environmental hormones can directly act on the central nervous endocrine regulatory system, causing紊乱 in the secretion of reproductive hormones, resulting in decreased fertility and abnormal embryonic development. Environmental factors that can cause abortion are diverse, including physical factors such as X-rays, microwaves, noise, ultrasound, and high temperatures, as well as heavy metals such as aluminum, lead, mercury, and zinc that affect the implantation of the fertilized egg or directly damage the embryo, leading to abortion. Various chemical drugs such as dichloropropane, carbon disulfide, anesthetic gases, oral antidiabetic drugs, and so on can interfere with and damage reproductive function, causing embryo abortion, stillbirth, malformation, developmental delay, and dysfunction. Unhealthy habits such as smoking, excessive alcohol consumption, coffee, drugs, and certain medications also affect the early embryonic development.
