Spontaneous miscarriage is when the embryo stops developing before the 28th week of gestation or is spontaneously expelled from the uterus. If spontaneous miscarriage occurs twice or more, it is called recurrent miscarriage; if it occurs three times or more, it is called habitual miscarriage. The incidence of spontaneous miscarriage is about 15%, recurrent miscarriage is about 5%, and habitual miscarriage is about 0.5%. Miscarriages that occur before 13 weeks of gestation are early miscarriages, while those that occur after 13 weeks of gestation are late miscarriages.
The causes of spontaneous miscarriage are complex and include: anatomical abnormalities of the uterus, genetic factors, endocrine disorders, and infections. The rapid development of reproductive immunology in recent years has revealed that most recurrent miscarriages of unknown origin in the past were due to immune disorders. Recent clinical observations have also revealed that prethrombotic states can also lead to recurrent miscarriages. People who suffer from recurrent miscarriages are not only financially, physically and emotionally devastated, but often the stability of the marriage and family is also shaken.
As the number of miscarriages increases, the condition becomes more severe, making the recurrence rate of miscarriage higher and higher. For example, the recurrence rate is 25% for those who have had one miscarriage, 30% for two miscarriages, 35% for three miscarriages, and more than 50% for four miscarriages. In view of the fact that there is no particular clinical manifestation to distinguish recurrent miscarriage from different causes, a comprehensive and systematic examination is often required for the diagnosis to clarify the causes and to provide targeted treatment.
Cause I. Immune disorders
More than 60% of recurrent miscarriages are due to immune disorders, and before the establishment of reproductive immune testing methods, the results of these women’s examinations in hospitals were almost “undetected abnormalities”, and thus they were not treated accordingly and effectively. Recent developments in this field have revealed that immune miscarriages include both alloimmune disorders and autoimmune abnormalities, the former being due to high compatibility of the couple’s leukocyte antigens and the failure of the mother to produce protective “closed antibodies” to the embryo after conception, and the embryo is attacked by the mother’s immune cells and stops being born. For treatment, the husband’s lymphocytes can be used to actively immunize the wife to produce closed antibodies. The latter is due to the disruption of the patient’s own immune system, which produces a variety of antibodies against its own tissues and organs, which can also destroy the embryonic tissue and the placental cells that nourish the embryo, leading to its death. Treatment can be done with corticosteroids and immunoglobulins. The success rate of treatment for these patients has reached more than 90%.
Cause 2: Genetic factors
Chromosomal abnormalities of the couple
Although chromosomal abnormalities in couples account for only about 5-8% of habitual miscarriages, there is no effective treatment yet, thus the recurrence rate is very high and only about 20% of successful pregnancies, and half of these offspring carry the abnormal chromosomes of their parents. Common chromosomal abnormalities include balanced translocations and inversions. There have been cases of up to six consecutive miscarriages in patients with balanced translocations. However, it is worth noting that these patients may have a combination of immune disorders, which need to be checked at the same time to avoid the possibility of not keeping a normal fetus.
Fetal chromosomal abnormalities
Fetal chromosomal abnormalities are caused by errors in the chromosomes of the fertilized egg during the process of division after conception, and the abnormal development and cessation of development of these fetuses is a natural process of elimination, which can be confirmed by the culture of the chorionic villi of the abortion. Chromosomal abnormalities have been reported in the majority of embryos with episodic miscarriage (first miscarriage).
Genetic abnormalities
The diagnosis of genetic abnormalities is currently difficult.
Cause III. Endocrine abnormalities
Gynecological endocrine abnormalities: common ones are luteal insufficiency, hyperprolactinemia, polycystic ovary syndrome, etc. In women with luteal insufficiency, after pregnancy, the ovaries cannot produce enough progesterone to support the normal development of placental cells, and the embryo does not get enough nutrition and dies, which is manifested by slow rise in basal body temperature after ovulation, fluctuation, or insufficient height and short time limit, and low progesterone level, treatment is relatively simple, progesterone supplementation is the most effective method, and the dosage and The dosage and treatment course can be adjusted according to the level of progesterone in blood after conception. Excessive prolactin mostly leads to non-ovulation and infertility, and even after conception, it is easy to miscarry, therefore, targeted treatment and fetal preservation must be given. Polycystic ovary syndrome is also often the cause of infertility and miscarriage, and aggressive fertility preservation therapy is very important in these women after conception. There have been cases of miscarriage in such patients after arduous treatment to conceive, due to neglect of fetal preservation, which can be followed by repeated treatment without further conception.
Endocrine abnormalities in internal medicine: mainly diabetic women and patients with abnormal thyroid function (including hyperthyroidism and hypothyroidism), if women with these diseases have been found, they should be treated until their condition is stable before considering pregnancy to avoid miscarriage. On the other hand, women with recurrent miscarriages should undergo relevant examinations in this regard to avoid missing the diagnosis.
Reason 4: Late occurrence of anatomical miscarriage
Uterine anatomical abnormalities lead to recurrent miscarriages accounting for about 10%-15% of miscarriages, which are characterized by mostly late miscarriages and embryos that are still alive at the time of miscarriage. The common causes are: cervical insufficiency, uterine developmental abnormalities (such as longitudinal uterus, unicornuate uterus, bicornuate uterus, saddle-shaped uterus, etc.), uterine fibroids or adenomyoma, and uterine adhesions. Diagnosis mainly relies on ultrasound, hysterosalpingography, hysteroscopy, laparoscopy and other examinations. Treatment depends on the specific cause of surgical correction, hysteroscopic surgery, or post-pregnancy cervical cerclage.
Cause V. Bacterial infection
Infections are common and indeterminate
Patients with recurrent miscarriage have a high positive rate of about 50% for various infections of the reproductive tract, such as Mycoplasma solium and Chlamydia infections, bacterial vaginosis, Candida vaginitis, leukocytosis and poor cleanliness of vaginal secretions. However, these infections are not necessarily the cause of recurrent miscarriage, nevertheless, these women should be excluded and treated before conceiving again.
Cause 6: Pre-thrombotic state should be taken seriously
Some women have a congenital or acquired disorder of blood clotting mechanism that causes their blood to clot too quickly, called pre-thrombotic state. Although normally there is no clotting in the blood vessels to form a thrombus, after pregnancy, these women have thrombus formation in the placental vessels, blocking the blood circulation of the placenta and causing the embryo to die from ischemia. In the past, not enough attention was paid to recurrent miscarriage due to this condition, but recent studies have found that many of the recurrent miscarriages of unknown origin are due to a pre-thrombotic state, and anticoagulant therapy has had a good effect.