Recurrent miscarriage is defined as 2 or more consecutive spontaneous abortions. Miscarriage is defined as termination before 28 weeks of gestation with a fetus weighing less than 1000 grams. Recurrent miscarriage is a common problem seen in approximately 1% of women of childbearing age.
Recurrent miscarriages mainly include chromosomal abnormalities, uterine anatomical abnormalities, infectious factors, endocrine abnormalities, pre-thrombotic states, and immune disorders. In 40%-60% of these cases, the cause is unknown, which is clinically known as “recurrent miscarriage of unknown origin”. In recent years, most of the unexplained recurrent miscarriages are related to abnormal immune function.
(A) Chromosomal factors
This includes chromosomal abnormalities in both spouses or embryos.
1. Chromosomal abnormalities in couples.
The incidence of chromosomal abnormalities in the normal population is about 0.5%, and the incidence of chromosomal abnormalities in one of the couples with recurrent miscarriage is about 2%-8%, among which the incidence of chromosomal abnormalities in the female is 2 times higher than that in the male.
2. Embryonic chromosomal abnormalities.
According to statistics, 46%-54% of spontaneous miscarriages are related to embryonic chromosomes. The earlier the miscarriage occurs, the higher the chance of embryonic chromosomal abnormalities, accounting for about 53% in early miscarriage and 36% in late miscarriage.
(ii) Uterine anatomical abnormalities
Recurrent miscarriage caused by anatomical abnormalities of the uterus accounts for 12%-15%, including various congenital malformations of the uterus, uterine adhesions, uterine fibroids or adenomyosis, and cervical insufficiency. Most recurrent miscarriages due to these factors are late (often occurring after 13 weeks) or premature, with relatively fresh embryonic tissue at the time of miscarriage. If the relevant factors are not corrected, the recurrence rate of miscarriage is higher.
1. Uterine malformations.
There are more types of uterine malformations, and the main ones associated with miscarriage are longitudinal uterus, bicornuate uterus, unicornuate uterus and uterine dysplasia.
2, uterine cavity adhesions.
It refers to the mutual adhesion of the uterine cavity and is seen in various causes of endometrial as well as myometrial damage. The main manifestations are reduced menstruation, even amenorrhea and symptoms of miscarriage and infertility.
3. Cervical insufficiency.
It is the phenomenon of pathological dilatation of the cervix in the non-delivery state caused by congenital or acquired abnormalities in the morphological structure and function of the endocervical opening, and is the cause of late recurrent miscarriage and preterm delivery. The incidence of cervical insufficiency in pregnant women is 0.05%-0.8%, rare in primiparous women and mostly in menstruating women. The causes are: cervical injury during delivery, post-cervical conization, cervical dysplasia, etc.
(iii) Infectious factors
A variety of pathogenic infections in the female reproductive tract can cause spontaneous abortion. Common pathogens include mycoplasma, chlamydia, toxoplasma, gonococcus, herpes simplex virus, rubella virus, cytomegalovirus, etc.
(iv) Endocrine abnormalities
Recurrent miscarriage due to endocrine abnormalities accounts for about 12%-15%, mainly due to gynecological endocrine abnormalities, such as luteal insufficiency, polycystic ovary syndrome, hyperprolactinemia, etc. Serious endocrine disorders can also lead to miscarriage, such as diabetes, hyperthyroidism or hypothyroidism, etc.
(E) Pre-thrombotic state
Pre-thrombotic state refers to a pathological process in which the hemostasis, coagulation, anticoagulation and fibrinolytic system are dysfunctional or impaired due to various factors. According to the different causes, it is divided into two categories: hereditary and acquired.
1.Hereditary pre-thrombotic state.
Including protein S and protein C deficiency, etc.
2.Acquired thrombophilia.
It refers to antiphospholipid syndrome and acquired homocysteinemia, etc.
(F) Immune disorders
Recent studies in reproductive immunology have shown that 50%-60% of the causes of recurrent miscarriage are related to immune disorders. With the development of research on the mechanism of immune recurrent miscarriage and treatment, the success rate of treatment is now over 90%.
1. Autoimmune recurrent miscarriage.
It is mainly seen in three diseases: antiphospholipid antibody syndrome, systemic lupus erythematosus, and dry syndrome. The common auto-principles are the three auto-antibodies associated with them: antiphospholipid antibody, anti-nuclear antibody, and anti-nuclear antibody extract.
2. Alloimmune recurrent abortion.
Refers to abnormal maternal recognition of the paternal antigen of the embryo, resulting in immune hyporesponsiveness, leading to a lack of maternal closed and/or protective antibodies, producing abnormal cellular and humoral immunity, and causing miscarriage due to the attack of the embryonic immune system.
(vii) Other female-related factors
In addition to the 6 major recurrent miscarriage related etiologies described above, other factors are also affected
1. Adverse factors in the environment.
Such as excessive exposure to harmful chemicals, excessive exposure to radiation, severe noise and vibration
2, adverse psychological factors.
Such as women’s mental tension, high depression, serious negative emotions, poor emotional control, fear of another pregnancy, nervousness, sadness and other adverse psychological stimuli through the neuroendocrine hormone system, so that the internal environment changes, can affect the normal development of the embryo.
3, excessive physical labor, alcoholism, smoking, drug addiction and other bad habits.
(H) Male factors
It mainly includes male chromosomal factor, sperm factor, male age, external exposure factor, etc.