Viral infections as the cause of embryo and fetopathies
Last reviewed: 23.04.2024
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The role of infection in the structure of perinatal mortality and morbidity, as well as in miscarriage of pregnancy is great.
However, not all infections are equally dangerous for the developing fetus. For example, influenza or other types of so-called acute respiratory infections (ARI) quite often affect pregnant women, but very rarely they are the cause of embryo or fetopathy (pathology of the embryo or fetus). But rubella, which occurs quite rarely, causes violations in the development of the fetus in almost 70% of cases.
The severity of the infectious lesion and its character largely depend on the stage of intrauterine development at the time of infection. And, depending on this, infectious embryos and fetopathies caused by infection are distinguished.
Infectious embryopathy occurs during periods of organogenesis (laying of organs) and placentation (formation of the placenta), corresponding to the first three months of pregnancy. It is very important that during this period the fetus lacks protective reactions to the introduction of infectious agents. This causes either death of the fetus, or the development of various deformities. Especially often, embryopathy develops in some viral infections, as the viruses are intracellular parasites and especially successfully develop in embryonic tissues.
Beginning with the fourth month and up to the period of childbirth, the disorders occurring in the fetus are called fetopathies.
Which infectious agents are most dangerous for the developing fetus? One of the leading places in the development of embryo or fetopathy belongs to a viral infection. True, it should be repeated that not all viruses, but a certain part of them are dangerous for the developing embryo (rubella virus, cytomegalovirus, herpes simplex virus, HIV).
The introduction of such viruses into the mother and fetus can have different consequences: it is either fetal death in the early or late stages of development (abortion), or various developmental defects that are compatible or incompatible with life, or the development of intrauterine infections that are already detected in the newborn.
Interestingly, embryo or fetopathy can occur even in the absence of direct primary infection of the fetus. Apparently, in this case several other damaging factors come into play: fever, intoxication, circulatory disorders in the mother. This leads to the development of inflammatory processes (focal or generalized) and hypoxia, which is no less important factor in affecting the embryo (influenza, measles, viral hepatitis, toxoplasmosis, tuberculosis, syphilis, listeriosis, sepsis). In addition, the degree of fetal damage does not always correspond to the severity of the disease in the mother. This is confirmed by clinical observations when, during mild disease, the mother experienced severe changes in the fetus and, conversely, in case of severe disease in the mother, the fetal lesion was minimal or not observed at all.
Rubella during pregnancy
Now let's proceed to the description of specific viral infections, among which the most dangerous for an embryo is the rubella virus. This disease, which in children (and adults) causes minimal disorders (rash, fever and slight malaise), the fetus can cause very serious violations, up to the formation of congenital malformations and even death. And the severity of the lesion depends on the stage of intrauterine development at the time of infection: if the infection occurred in the first two months of pregnancy, the probability of infection of the fetus is 70-80%, if at 3 months - about 50%. Later, there is a sharp decrease in the frequency of intrauterine fetal damage.
The virus, getting into the body of a pregnant woman, accumulates in the placenta and comparatively quickly affects the epithelium of villi and fetal vessels. After this, the endocardium (inner shell of the heart) of the fetus begins to suffer. In the future, other organs and tissues become infected. The infection becomes chronic.
If the fetus does not die in utero, then it can develop the following developmental defects: congenital heart defects, deafness, blindness, central nervous system damage (microcephaly). If the infection of the fetus occurred later (after 12-16 weeks), it may be accompanied by the appearance of a typical "rubella" rash in the newborn, which, however, disappears quite quickly.
Given that embryo and fetopathy with rubella occur very often, it is necessary to abort pregnancy artificially, that is, to make an artificial abortion. Some authors recommend the introduction of gamma globulin for the prevention of embryopathies in cases of rubella infection in a pregnant woman. But still the bulk of researchers believe that the risk of an ugliness, even with the introduction of this drug, remains high, and it is better to terminate pregnancy.
Cytomegalovirus infection during pregnancy and its effect on the fetus
The cytomegalic virus is no less dangerous for the fetus, given its prevalence among pregnant women (up to 6%). And it is established that pregnancy activates latent cytomegaly. This is confirmed by the fact that in non-pregnant women the cytomegalovirus is detected only in 1.8% of cases. With cytomegaly, the fetus is affected not only transplacental, but also through an ascending infection: from the vagina to the cervix, and then into the uterus. The virus of cytomegaly is still more dangerous in case of primary infection during pregnancy. The latent infection of the mother is less dangerous for the fetus.
Like the rubella virus, the cytomegalovirus in the early stages of development leads to fetal death and spontaneous abortion. If the infection occurred at the stage of organ formation, neonates may experience hepato-splenomegaly (enlargement of the liver and spleen), microcephaly, hydrocephalus, mental disorders, various rashes, eye injuries and other injuries of various organs and tissues.
The danger of cytomegaly lies in the fact that it is difficult to diagnose it. But if the disease was diagnosed in the first months of pregnancy, then in order to avoid the above problems pregnancy is recommended to be interrupted.
It should be said that the treatment of congenital cytomegaly with antibiotics or sulfonamides, according to the published data, is ineffective.
[Herpes and pregnancy
Among the viruses that are dangerous for the fetus and newborn, it should also be noted and herpes simplex virus (urogenital herpes). Infection with this infection often occurs when the fetus passes through the birth canal of a mother who has herpes. Especially often this happens if a woman has been infected in recent weeks before giving birth.
The clinic of intrauterine infection usually manifests itself in the first weeks of life. Against the background of typical herpetic eruptions in the external genital area, severe general intoxication develops, jaundice, cyanosis, high fever, respiratory failure, convulsions, hemorrhagic eruptions. Urogenital herpes (HIV-associated infection) can cause spontaneous abortions in pregnant women with this infection, fetus and newborn infection, causing teratogenic effects, even resulting in death.
Measles and pregnancy
Coronary disease in pregnant women is very rare, since most women are vaccinated or usually endure this infection in childhood. However, occasionally such cases occur. With this disease, spontaneous abortions and premature births sometimes occur.
But a child born to a mother who already had measles in childhood or adolescence acquires an inborn (passive) immunity to this disease, lasting about 3 months.
Chickenpox and pregnancy
Also, as with measles, it is rare that a disease with chickenpox occurs during pregnancy. And, as with measles, the causative agent of chicken pox is not transmitted through the placenta and does not cause ugliness in the fetus. But if a woman gets sick in the last weeks of pregnancy, intrauterine infection can occur, which occurs in a newborn on the 5th-10th day of life in the form of typical wind-choked inflammations.
Influenza during pregnancy and its effect on the fetus
Of particular interest is the influence of the influenza virus on the course of pregnancy and the developing fetus. Moreover, in addition to influenza, in the autumn-winter-spring periods, the population often suffers from so-called respiratory infections, which include: parainfluenza, respiratory syncytial, adenovirus, etc. In many respects, their clinical manifestations are so similar that it is accurate to say which of them pregnant, almost impossible. Unless to resort to virological researches. But, nevertheless, to know whether the flu is another respiratory infection is necessary. This is due to the fact that colds, although they can contribute to an increase in the incidence of miscarriage and stillbirths, but do not cause malformations of the fetus.
Against the background of increased incidence of influenza, the incidence of miscarriages and stillbirths may increase. Children often quite often have various developmental abnormalities: congenital cataracts (clouding of the lens of the eye), clitoral anomalies in girls, hypospadias in boys (abnormal placement of the urethra on the penis), cleft lip, wolf mouth,
And although the transmission of the influenza virus through the placenta has not been fully proven, the above facts indicate that the flu is a much more serious disease than just a cold. But, since there is no evidence of placental infection of the fetus yet, it can be assumed that the developmental fetal malformations and all other unfavorable outcomes of pregnancy are due to the fact that the blood vessels suffer primarily from blood, there is a significant intoxication and the temperature rises significantly, which leads to violation of utero-placental circulation, small hemorrhages and, in the final analysis, fetal hypoxia.
Prevention of influenza, and other respiratory infections, is hardening, the use of vitamins (especially C and P), compliance with anti-epidemic measures (ventilation of premises, wearing gauze dressings, refusing to visit places with large concentrations of people, etc.). During influenza outbreaks, it is advisable to immunize with influenza vaccine.
Viral hepatitis during pregnancy
An important role in the pathogenesis of intrauterine damage to the fetus belongs to viral hepatitis. Viral hepatitis A is a very common infectious disease transmitted by the fecal-oral route (through the mouth). It affects almost all segments of the population, and pregnant women do not constitute exceptions. Moreover, in pregnant women this disease often takes place more heavily, with pronounced intoxication and metabolic disorders, having a negative effect on the condition of the fetus and the newborn. Moreover, the fetus is affected both by the severe condition of the mother, and by the virus itself, which penetrates the placenta both in the early and late stages of pregnancy. The virus causes widespread plaque inflammation, villous dystrophy, circulatory disorders and other pathological changes in the placenta.
In newborns, intrauterine infection can lead to the onset of congenital viral hepatitis, often (with untimely and inaccurate treatment) resulting in cirrhosis of the liver.
Such children develop poorly, later they start talking, sometimes there are mental disorders. These disorders are not related to the specific effect of the hepatitis virus and are a manifestation of general intoxication and hypoxia in this disease in the mother.
Prevention of both viral hepatitis A and viral hepatitis B (transmitted by contact with the blood of a patient during blood transfusions, through poorly processed surgical or dental instruments) is the observance of sanitary and epidemiological standards.