Patient's question:
I had a miscarriage before, and now I'm pregnant again, so I'm being very careful. Since I found out I was pregnant, I quit my job and am taking good care of myself at home, but sometimes I still worry. I want to know what can cause a miscarriage in the early stages of pregnancy!Doctor's answer:
What are the causes of embryonic arrest? Embryonic arrest refers to the cessation of development of the embryo in the early stages of pregnancy due to certain reasons. Ultrasound examination shows irregular morphology of the fetal bud or fetus within the gestational sac, without fetal heartbeat, or it may appear as atrophy of the gestational sac. Clinically, it falls under the category of miscarriage or stillbirth. There are many reasons that can lead to embryonic arrest. [2] (1) Endocrine disorders: Embryonic implantation and continued development depend on the coordinated interaction of a complex endocrine system. Any disruption in this system can lead to miscarriage. During early embryonic development, three important hormone levels are required: estrogen, progesterone, and human chorionic gonadotropin. From the mother's perspective, if her endogenous hormone levels are insufficient, they may not meet the needs of the embryo, potentially leading to embryonic arrest and miscarriage. The most common cause is luteal dysfunction. Luteal insufficiency can result in delayed endometrial development and a short luteal phase, thereby affecting the implantation of the fertilized egg or early pregnancy miscarriage. Individuals with luteal insufficiency often have other glandular dysfunctions, such as hyperthyroidism or hypothyroidism, diabetes, relative androgen excess, and hyperprolactinemia. These factors are all detrimental to embryonic development and are closely related to miscarriage. (2) Immunological factors: The intrauterine embryo or fetus is essentially an allogeneic transplant because the fetus is a combination of genetic material from both parents and cannot be entirely identical to the mother. Immune incompatibility between the mother and fetus can lead to rejection of the fetus by the mother. Common autoimmune diseases include systemic lupus erythematosus, scleroderma, mixed connective tissue disease, and dermatomyositis. The second issue is reproductive immunity. If a person carries certain antibodies, it may affect embryonic development. In reality, antibody testing varies from hospital to hospital, and doctors have differing opinions. From a research perspective, four factors are considered influential: one is antisperm antibodies, which, if present, may hinder fertilization; second, antierosal antibodies, which, if present, may affect embryonic development and resist it; third, antiovarian antibodies, which, if present, may affect the quality of the eggs; and fourth, antihCG antibodies, which are an important hormone that is secreted seven days after fertilization. However, if a person carries this antibody, it may inhibit hormone secretion, potentially leading to embryonic arrest. (3) Uterine abnormalities: The internal and overall environment of the uterus can affect the embryo. The internal environment refers to the endometrium. If it is too thin or too thick, it can affect implantation. Miscarriages caused by uterine defects account for approximately 10% to 15%. Common abnormalities include (1) congenital abnormalities of the Müllerian ducts, including unicornuate uterus, bicornuate uterus, and didelphic uterus, leading to a narrowed uterine cavity and restricted blood supply. Abnormal development of uterine arteries can lead to asynchronous decidualization and abnormal implantation. (2) Uterine adhesions, primarily caused by uterine trauma, infection, or residual placental tissue, leading to uterine adhesions and fibrosis. This hinders normal decidualization and placental implantation. (3) Uterine fibroids and endometriosis can reduce blood supply, leading to ischemia and venous dilation, asynchronous decidualization, abnormal implantation, and hormonal changes caused by fibroids can also lead to pregnancy failure. (4) Congenital or traumatic cervical incompetence, as well as abnormal cervical development due to exposure to diethylstilbestrol in utero, often result in miscarriage in the second trimester. (4) Chromosomal issues: Chromosomal abnormalities can also lead to early miscarriage due to the failure of embryonic development. Chromosomal abnormalities include numerical and structural abnormalities. Numerical abnormalities can be divided into aneuploidy and polyploidy, with the most common abnormal karyotype being triploidy, and trisomy 16 accounts for one-third, often being lethal. Trisomy 21 includes 25% to 67%, trisomy 13 includes 4% to 50%, and trisomy 18 includes 6% to 33%, all of which inevitably lead to miscarriage. Other abnormalities include monosomy (4SX) and tetrasomy due to abnormal cleavage, leading to non-development of the embryo. Structural abnormalities include deletions, balanced translocations, inversions, and duplications. Balanced translocations are the most common chromosomal abnormalities. Regarding chromosomal issues, current research suggests that chromosomes pair, exchange, and separate to form gametes, which then combine to form zygotes. If any of these zygotes are abnormal, it can lead to abnormal development, resulting in miscarriage, stillbirth, stillbirth, or malformed infants. Therefore, prenatal diagnosis is necessary to prevent the birth of chromosomal children. Currently, Western medicine has no effective treatment for miscarriages or embryonic arrests caused by chromosomal abnormalities, and only prenatal genetic counseling and diagnosis can be performed. Theoretically, individuals with chromosomal abnormalities have the opportunity to give birth to normal nuclear type and carrier infants. Prenatal diagnosis for these couples ensures the birth of normal infants. However, current research also indicates that even if both partners have normal chromosomes, chromosomal abnormalities can occur during gamete formation or embryonic development. For example, if a woman is over 35 years old, her eggs may age, leading to chromosomal non-separation and abnormal chromosomal development. Abnormal semen, such as sperm with large heads, is mostly diploid, and after fertilization, it forms polyploid embryos, leading to miscarriage. Exposure to adverse environmental factors, such as toxic chemicals, radiation, and high temperatures, can also cause chromosomal abnormalities in embryos. Therefore, the key to preventing embryonic arrest caused by chromosomal abnormalities is to regulate the health of both partners, ensuring that their organ functions are normal and balanced, and to choose the best time to conceive while avoiding adverse environments. (5) Reproductive tract infections: In addition to the various factors mentioned above, infections caused by early pregnancy miscarriage are increasingly being recognized by scholars both domestically and internationally. Severe TDRCH infections in the early stages of pregnancy can cause embryonic death or miscarriage, while mild infections can also cause embryonic malformations. Research shows that cytomegalovirus can cause delayed miscarriage, intrauterine fetal death, etc. After the mother becomes infected, pathogens can enter the placenta through the bloodstream, damaging the chorion and capillary endothelium, disrupting the placental barrier, and entering the fetus, leading to miscarriage, embryonic arrest, and fetal malformations. In recent years, many studies have shown that mycoplasma infections are associated with embryonic arrest. The positive rate of mycoplasma infections in cervical secretions of women with embryonic arrest is significantly higher than that of normal women, with a highly significant difference. (6) Environmental factors: Changes in physiological status during pregnancy alter the mother's absorption, distribution, and excretion of therapeutic drugs and various environmental harmful substances. In the early stages of development, the embryo is highly sensitive to the effects of therapeutic drugs and environmental factors. At this stage, various harmful factors can cause embryonic damage or even loss. Many drugs and environmental factors are important causes of early embryonic death or fetal malformations. Environmental hormones can directly act on the central nervous system and endocrine regulatory system, causing disorders in reproductive hormone secretion, leading to reduced fertility and abnormal embryonic development. Environmental factors that can cause miscarriage are diverse, including physical factors such as X-rays, microwaves, noise, ultrasound, and high temperatures, as well as heavy metals like aluminum, lead, mercury, and zinc, which can affect fertilized egg implantation or directly damage the embryo, leading to miscarriage. Various chemical drugs, such as dibromopropene, carbon disulfide, anesthetic gases, and oral antidiabetic drugs, can interfere with or damage reproductive function, leading to embryonic miscarriage, stillbirth, malformations, delayed development, and functional disorders. Poor lifestyle habits, such as smoking, excessive alcohol consumption, caffeine, drugs, and certain medications, also affect early embryonic development. Symptoms of early embryonic arrest If embryonic arrest occurs, all pregnancy symptoms in the mother will gradually disappear. First, there will be no more nausea, vomiting, or other early pregnancy symptoms, and the feeling of breast fullness will also weaken. Then, there may be vaginal bleeding, often dark red and watery. Finally, there may be lower abdominal pain, and the embryo may be expelled. These symptoms vary from person to person, and some may even show no signs at all, directly experiencing abdominal pain and then miscarriage, or having embryonic arrest with no symptoms, which is discovered through routine ultrasound examination. Early diagnosis of embryonic arrest 1. Symptoms: Most women experience no obvious symptoms after fetal arrest, while some may have spotting. Generally, there is no abdominal pain, which is different from threatened miscarriage. 2. Diagnosis: Patients with a history of missed periods should undergo early ultrasound examination, regardless of whether spotting occurs, to avoid missing a diagnosis of embryonic arrest. Ultrasound monitoring of embryonic and fetal development can help diagnose abnormalities. If there is no gestational sac at ≥6 weeks, or if the gestational sac is deformed and shrunk, and if the gestational sac is ≥4 cm but no embryo is visible, or if the embryonic head and limb length is ≥1.5 cm but there is no fetal heartbeat, it can be determined that the embryo or fetus has developed abnormally. The latter three conditions can be diagnosed as embryonic arrest. Additionally, blood β-hCG measurement can also help in the diagnosis of embryonic arrest. If there is ≥5 weeks, blood β-hCG