Among the patients who come to the center, there is a group of people who are not unable to conceive, but just can’t keep each pregnancy, always stopping at one or two months, or having a spontaneous miscarriage in the middle of pregnancy, becoming discouraged after experiencing several times from joy to disappointment, and some of them even start to use contraception. It is also called habitual miscarriage.
Recurrent miscarriage is defined as three or more fetal losses before the 28th week of gestation. In the United States, 2 consecutive failed pregnancies are considered recurrent miscarriages.
I. Incidence
The clinical incidence of spontaneous abortion is 15% to 25%, and more than 80% of them are early abortions that occur before the 12th week of gestation. Patients with two or more miscarriages account for about 5% of women in their reproductive years.
The percentage of patients with 3 or more miscarriages is about 1%.
The risk of recurrence of RSA increases with the number of miscarriages, and studies have shown that a history of previous spontaneous abortion is an independent risk factor for subsequent pregnancy failure.
Patients with a history of more than 3 consecutive spontaneous abortions have an embryo loss rate of nearly 40% after a second pregnancy. In addition, maternal age and obesity are also high-risk factors for spontaneous abortion.
Etiology
The etiology of RSA is very complicated, mainly including genetic factors, anatomical factors, endocrine factors, infectious factors, abnormal immune function, pre-thrombotic state, maternal systemic diseases and environmental factors.
Miscarriage occurs before 12 weeks is called early miscarriage; 12 weeks to 28 weeks is called late miscarriage.
1.Anatomical structure factors
Including various congenital malformations of the uterus, cervical insufficiency, uterine adhesions, uterine fibroids, uterine adenomyosis, etc. The rate of miscarriage or preterm delivery will be significantly higher in women with untreated uterine anomalies when they have another pregnancy, and cervical insufficiency is an important cause of late spontaneous abortion.
2. Pre-thrombotic state
At present, it is generally believed that the hypercoagulable state during pregnancy changes the state of blood flow in the uteroplacental area, which is easy to form local microthrombosis and even cause placental infarction, resulting in the decrease of blood supply to the placental tissue, embryo or fetus ischemia and hypoxia, and finally leads to the miscarriage of embryo or fetus with poor development.
3.Genetic factors
Chromosomal abnormalities of the couple: including chromosomal translocation, chimerism, deletion or inversion, etc. Chromosomal abnormalities in the parental generation may lead to failure to produce normal gametes, failure of fertilization or abnormal differentiation and development of the embryo after fertilization, etc. Embryonic chromosomal abnormalities: It is the most common cause of RSA. The earlier the miscarriage occurs, the higher the probability of its embryonic chromosomal abnormalities, and the embryonic chromosomal abnormalities can directly lead to developmental failure and miscarriage.
4.Endocrine factors
Polycystic ovary syndrome (PCOS), hyperprolactinemia and other endocrine diseases such as uncontrolled diabetes mellitus and thyroid disease are related to the occurrence of RSA.
5. Infection factors
Systemic infections and reproductive tract infections can cause spontaneous abortion or RSA, depending on the infection. Bacterial vaginosis is a high-risk factor for late miscarriage and preterm delivery.
6. Immune factors
Antiphospholipid syndrome (APS) is one of the most important and treatable causes of RSA. Clinical manifestations include arteriovenous thrombosis, pathological pregnancy, and reduced platelet count, and APS is closely related to the prethrombotic state. Immune abnormalities also include many other currently unspecified conditions, often referred to as “unexplained recurrent abortions” (URSA). Sequestering antibody deficiency, NK
cell number and activity may be closely related to URSA.
7.Other adverse factors
Environmental factors, psychological factors, excessive physical labor, smoking, alcohol abuse, excessive coffee consumption, drug abuse and drug addiction can all affect female fertility. For patients with RSA, special attention should be paid to psychological well-being. Mental tension, negative depression, as well as fear, sadness and other adverse psychological stimuli can affect the neuroendocrine system and make changes in the internal environment of the body, thus affecting the normal development of the embryo.
8. Age and total number of previous abortions
The British expert consensus also considers age and total number of previous abortions as one of the important factors of RSA, the older the age, the higher the risk of RSA; the more the total number of previous abortions (including accidental abortions and induced abortions), the higher the risk of RSA.
III. Treatment
The etiology and mechanism of recurrent miscarriage is very complex and varies from patient to patient. Only when the etiology is determined through systematic screening can the corresponding treatment be given. Most of the RSA can be treated well after the etiology is determined, but there are some patients with RSA of unknown cause who have little effect with the current examination and treatment.