Viral infections as a cause of embryo- and fetopathies

The role of infection in the structure of perinatal mortality and morbidity, as well as in miscarriage, is great.

However, not all infections are equally dangerous for the developing fetus. For example, flu or other types of so-called acute respiratory infections (ARD) quite often affect pregnant women, but very rarely they cause embryo or fetopathy (pathology of the embryo or fetus). But rubella, which is quite rare, causes developmental disorders in the fetus in almost 70% of cases.

The severity of the infectious lesion and its nature largely depend on the stage of intrauterine development at the time of infection. And depending on this, infectious embryopathies and fetopathies caused by infection are distinguished.

Infectious embryopathies occur during the periods of organogenesis (organ formation) and placentation (placenta formation), corresponding to the first three months of pregnancy. It is very important that during this period the fetus has no protective reactions to the introduction of infectious agents. This causes either the death of the fetus or the development of various deformities. Embryopathies develop especially often with some viral infections, since viruses are intracellular parasites and develop especially successfully in embryonic tissues.

Starting from the fourth month and up until the period of childbirth, disorders that occur in the body of the fetus are called fetopathies.

What infectious agents are the most dangerous for the developing fetus? One of the leading places in the development of embryo or fetopathy belongs to viral infection. However, 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 bodies of the mother and fetus can have various consequences: either the death of the fetus in the early or late stages of development (abortion), or various developmental defects compatible or incompatible with life, or the development of intrauterine infections that are detected already in the newborn.

It is interesting that embryo- or fetopathy may 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 an equally important factor in the damage of the embryo (flu, measles, viral hepatitis, toxoplasmosis, tuberculosis, syphilis, listeriosis, sepsis). In addition, the degree of damage to the fetus does not always correspond to the severity of the disease in the mother. This is confirmed by clinical observations, when with a mild course of the disease in the mother, severe changes were observed in the fetus and, conversely, with a severe course of the disease in the mother, damage to the fetus was minimal or not observed at all.

Rubella during pregnancy

Now let's move on to a description of specific viral infections, among which the most dangerous for the embryo is the rubella virus. This disease, which in children (and adults) causes minimal disturbances (rash, fever and slight malaise), can cause very serious disturbances in the fetus, up to the formation of congenital malformations and even death. Moreover, 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, then the probability of infection of the fetus is 70-80%, if in the 3rd month - about 50%. Later, a sharp decrease in the frequency of intrauterine fetal damage is observed.

The virus, entering the body of a pregnant woman, accumulates in the placenta and relatively quickly affects the epithelium of the villi and vessels of the fetus. Following this, the endocardium (the inner lining of the heart) of the fetus begins to suffer. Subsequently, other organs and tissues become infected. The infection becomes chronic.

If the fetus does not die in utero, the following developmental defects may develop: congenital heart defects, deafness, blindness, damage to the central nervous system (microcephaly). If the fetus is infected at a later stage (after 12-16 weeks), it may be accompanied by the appearance of typical "rubella" rashes in the newborn, which, however, disappear quite quickly.

Considering that embryo- and fetopathy with rubella occur very often, it is necessary to terminate the pregnancy artificially, that is, to have an artificial abortion. Some authors recommend administering gamma globulin to a pregnant woman to prevent embryopathies with rubella. However, the majority of researchers believe that the risk of deformities, even with the administration of this drug, remains high, and it is better to terminate the pregnancy.

Cytomegalovirus infection during pregnancy and its impact on the fetus

The cytomegalovirus is no less dangerous for the fetus, given its prevalence among pregnant women (up to 6%). Moreover, it has been established that pregnancy activates latent cytomegalovirus. This is confirmed by the fact that in non-pregnant women, the cytomegalovirus is detected only in 1.8% of cases. With cytomegalovirus, the fetus is affected not only transplacentally, but also by ascending infection: from the vagina to the cervix, and then to the uterus. The cytomegalovirus is still more dangerous in primary infection during pregnancy. 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 infection occurs at the stage of organ formation, then newborns may experience hepatosplenomegaly (enlargement of the liver and spleen), microcephaly, hydrocephalus, mental disorders, various rashes, eye damage and other damage to various organs and tissues.

The danger of cytomegalovirus is that its diagnosis is difficult. But if the disease was diagnosed in the first months of pregnancy, then in order to avoid the above-mentioned problems, it is recommended to terminate the pregnancy.

It should be said that treatment of congenital cytomegalovirus with antibiotics or sulfonamides, according to literary data, is ineffective.

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Herpes and pregnancy

Among the viruses that are dangerous for the fetus and newborn, it is also worth noting the herpes simplex virus (urogenital herpes). Infection with this infection most often occurs when the fetus passes through the birth canal of a mother who has herpes. This happens especially often if the woman is infected in the last weeks before giving birth.

The clinical picture of intrauterine infection usually manifests itself in the first weeks of life. Against the background of typical herpetic rashes in the area of the external genitals, severe general intoxication, jaundice, cyanosis, high temperature, respiratory failure, convulsions, hemorrhagic rashes develop. Urogenital herpes (HIV-associated infection) can cause spontaneous abortions in pregnant women suffering from this infection, infection of the fetus and newborn, having a teratogenic effect, even leading to death.

Measles and pregnancy

Measles is very rare in pregnant women, as most women are vaccinated or usually have the infection as children. However, it does occur occasionally. Miscarriages and premature births sometimes occur with this disease.

However, a child born to a mother who has already had measles in childhood or adolescence acquires innate (passive) immunity to this disease, which lasts for about 3 months.

Chickenpox and Pregnancy

Chickenpox is also rare during pregnancy, just like measles. And, like measles, the chickenpox pathogen is not transmitted through the placenta and does not cause deformities in the fetus. But if a woman gets sick in the last weeks of pregnancy, intrauterine infection may occur, which manifests itself in the newborn on the 5th-10th day of life in the form of typical chickenpox inflammations.

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Flu during pregnancy and its impact on the fetus

Of particular interest is the effect of the flu virus on the course of pregnancy and the body of the developing fetus. Moreover, in addition to the flu, in the autumn-winter-spring periods the population often suffers from so-called respiratory infections, which include: parainfluenza, respiratory syncytial, adenovirus, etc. In many ways, their clinical manifestations are so similar that it is almost impossible to say exactly which of them the pregnant woman has suffered. Unless you resort to virological studies. But, nevertheless, it is necessary to know whether it is the flu or another respiratory infection. This is due to the fact that colds, although they can contribute to an increase in the incidence of miscarriage and stillbirth, do not cause fetal malformations.

Against the background of increased flu incidence, the frequency of miscarriages and stillbirths may increase. Children often have various developmental anomalies: congenital cataracts (clouding of the lens of the eye), clitoral anomalies in girls, hypospadias in boys (incorrect positioning of the urethra on the penis), harelip, cleft palate, etc.

Although the transmission of the flu virus through the placenta has not been definitively 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 fetal malformations and all other adverse pregnancy outcomes are associated with the fact that with the flu, the blood vessels are primarily affected, severe intoxication occurs and the temperature rises significantly, which leads to disruption of the uteroplacental blood circulation, minor hemorrhages and, ultimately, to fetal hypoxia.

Prevention of influenza, as well as other respiratory infections, includes hardening, taking vitamins (especially C and P), and observing anti-epidemic measures (ventilating rooms, wearing a gauze bandage, avoiding crowded places, etc.). During influenza outbreaks, it is advisable to immunize with an influenza vaccine.

Viral hepatitis during pregnancy

Viral hepatitis plays an important role in the pathogenesis of intrauterine fetal damage. 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 are no exception. Moreover, in pregnant women, this disease often proceeds more severely, with pronounced intoxication and metabolic disorders, having a negative effect on the condition of the fetus and newborn. Moreover, the fetus is affected by both the severe condition of the mother and the virus itself, which penetrates the placenta in both the early and late stages of pregnancy. The virus causes widespread inflammation of the placenta, villous dystrophy, circulatory disorders and other pathological changes in the placenta.

In newborns, intrauterine infection can lead to the development of congenital viral hepatitis, which often (with untimely and inaccurate treatment) ends in liver cirrhosis.

Such children develop poorly, start talking later, and sometimes have mental disorders. These disorders are not associated with the specific action of the hepatitis virus and are a manifestation of general intoxication and hypoxia in the mother with this disease.

Prevention of both viral hepatitis A and viral hepatitis B (transmitted through contact with the blood of a sick person during blood transfusions, through poorly processed surgical or dental instruments) involves compliance with sanitary and epidemiological standards.