Pregnancy and infections

In most cases pregnancy is something highly anticipated and desired by both parents. This is a period filled with trepidation and excitement, but it is also full of unknowns, and to a certain extent agitations. This is a moment when pregnant women change some of their habits and keep themselves away from harmful things.

The most common worry during pregnancy are the various infections. I will pay attention to the most common of them – how they are transmitted, what are the consequences for the mother and the fetus, what tests we can do and how pregnant women must protect themselves as much as they can.

The most common viruses during pregnancy are cytomegalovirus (CMV), parvovirus B-19, rubella, varicella, and toxoplasma parasitosis. For the last two years, we have been overwhelmed by the Covid-19 pandemic, which I will address at the end.

Cytomegalovirus (CMV)

I start with the most common virus – cytomegalovirus (CMV), which is of the herpesvirus family. The frequency of this disease is 1% of all pregnant women, i.e. is a fairly common infection. But for our peace of mind, most women have had it in childhood and have built up an immunity to it. The virus is transmitted through close contact between people, through blood, during organ transplantation, sexual contact, from a pregnant woman to a fetus, and during breastfeeding. That is why pregnant women must observe good personal hygiene and wash their hands before eating. They should not use other people’s utensils, especially children’s (in a closed collectives of children the virus is spread quickly and easily), and they must not kiss children, especially when they are sick. CMV infection in an adult can be asymptomatic or with mild discomfort, fatigue, fever, sore throat and swollen lymph nodes. Basically like any mild viral infection. But unfortunately, this virus can have very serious consequences for the fetus, including deafness, impaired vision, liver changes, blood clotting disorders, neurological changes – epilepsy, mental retardation, and even loss of fetal tones. The earlier the infection occurs during pregnancy, the more severe the damage to the fetus.

During pregnancy, there may be various symptoms that may be indicative to examine the mother and the fetus for cytomegalovirus. It starts with blood tests on the pregnant woman, looking at the antibodies – IgM indicate a fresh, recent infection, while IgG are an indicator of an old infection.

Although the infection could be previous, we need to know how previous. To determine this, we study the tendency of antibodies to bind to foreign antigens, which is called avidity. In the diagnosis, we can include the examination of viral particles in the amniotic fluid, through amniocentesis, or the antibodies produced by the fetus, by taking blood from the umbilical cord – cordocentesis.

Depending on the results, the presence or absence of ultrasound indications and the wishes of the parents, the steps of diagnosis and behavior are determined. Treatment and prevention at this stage are still in the testing stage and are not widely applied.

Parvovirus B-19

Parvovirus B-19 (or fifth disease) is a DNA virus that most commonly occurs in childhood. It is transmitted by airborne droplets and touch. Children experience it as a rash on the face that progresses over the whole body. While adults suffer from joint pain. Unfortunately, there is a high rate of transmission to the fetus. This virus causes damage to various cells, but most often the red blood cells (erythrocytes), which are the cells that carry oxygen in our blood. Damage to them can be the cause of severe anemia. Other organs are heart tissue, but as an indirect consequence, the brain can also be damaged due to anemia. It can cause fatal fetal edema.

During pregnancy, we monitor for any signs of anemia (using Doppler US), and at a later stage, cardiac changes, edema and fluid collection in the chest, around the heart, in the abdomen.

In women who have suffered the infection, we examine the known IgM and IgG antibodies. The amniotic fluid and the fetal blood can be tested for the virus. Through cordocentesis, using blood from the umbilical cord, we examine the severity of the anemic syndrome of the fetus, but we also transfuse it. Fetal transfusion improves prognosis and allows time for fetal maturation before delivery.


Rubella is an RNA virus and is included in the immunization schedule in most countries. In Bulgaria, this is done at the thirteenth month after birth and re-immunization at the age of 12. The symptoms of the disease include general indisposition, fever, fatigue, followed by a fine rash all over the body and enlarged lymph nodes in typical places. Transmission to the fetus is very high, but decreases as pregnancy progresses until the beginning of the third trimester, when it again increases dramatically. The damage to the fetus is severe – impaired vision, hearing loss, heart abnormalities, fetal growth retardation, liver disorders and others. Unfortunately, not all signs of infection can be detected with ultrasound. IgM and IgG antibodies are tested (if the woman is immunized, she should have IgG antibodies), and for the diagnosis, the amniotic fluid is tested for viral particles.

The prognosis for infection in the early stage of pregnancy is not good, and termination of pregnancy is a possibility.


Varicella is a virus of the herpesvirus family. It has very high transmissibility rate, but most of the adult population has long-lasting immunity built up in childhood. Primary infection during pregnancy is rare, occurring in 2 in 1,000 pregnant women. Transmission of the virus to the fetus is low, less than 1% rate during the first trimester, and up to 20 weeks of gestation it is 2%, after which there is practically no transmission until the last weeks. After 36 weeks the fetus can be infected and the manifestation is a skin rash or chicken pox of the newborn. Congenital varicella infection can range in severity from skin lesions, blindness, limb disorders to brain damage and mental retardation. If serious abnormalities are established up to the 20th week of gestation, termination of pregnancy is discussed. But since such abnormalities after suffered infection are rare, it is recommended follow-up every 4 weeks.

This is an airborne infection and in order to protect ourselves we must keep isolation. Pregnant women who have not had varicella should suspend their work in nurseries, kindergartens, medical institutions and keep their children from visiting such institutions until at least to 20 weeks of gestation. The follow-up is done with ultrasound. Here diagnostics using amniocentesis should be very carefully considered and avoided if possible.


Toxoplasmosis is a parasitic disease caused by toxoplasma gondii. Infection is possible when eating undercooked meat or from objects contaminated by pets (cats and dogs), in case of poor hygiene. Here again, personal hygiene is very important to avoid infection. I would also advise avoiding contact with animals throughout the pregnancy, unless they already live in your home and never leave it. And yet – good hygiene! Of course, raw food eaters will have to avoid not only half-cooked meat, but also sushi.

With the progression of pregnancy, the chance of transmission of the infection to the fetus increases. The parasite can damage vision, cause hydrocephalus and damage the fetal nervous tissue.

Diagnosis sometimes can be challenging. Not always after positive IgM and IgG a subsequent amniocentesis can give reliable results. Treatment is with antibiotics. Termination of pregnancy is being considered.


In the past two years, we have been affected by Covid-19, a devastating pandemic that has put us to a number of tests – even moral and ethical, due to the presence of much speculation and misinformation. We are not yet fully certain whether this virus is transmitted from the mother to the fetus, but if it is, it is at a very low rate. However, this infection increases the risk of abortion, premature birth, and respiratory failure of the pregnant woman. Compliance with the anti-epidemic measures has proven to be a serious challenge for the health authorities due to the frequency of travel in the 21st century, the duration of the pandemic and the mental exhaustion of people, but also because of the strong “anti” propaganda. I really hope the end is near. The American College of Obstetricians and Gynecologists and the Royal College of Obstetricians and Gynecologists recommend full vaccination of women planning pregnancy, pregnant after 12 weeks of gestation and nursing mothers.

And one last advice from me: observe good personal hygiene, limit contact with people who are at risk of transmitting infections, use individual utensils and eat well-cleaned and cooked food, avoid close contact with animals, if necessary, wear a mask, for to protect yourself and your unborn child!

Author: Dr. Boris Stoilov


Center for Fetal Medicine

Get informed about the world of Fetal Medicine with Dr. Boris Stoilov.

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