Infections that may be dangerous to the fetus

Listeria bacteria can penetrate and infect the placenta, the amniotic fluid, and the fetus. The fetus may also be infected in the birth canal at childbirth, in which case the disease will not become apparent until days or weeks after birth. Listeria bacteria are not always passed from mother to fetus.

• Listeriosis is rare. Only a few cases of maternal listeriosis are found in Finland per year.
• Listeria does not cause birth defects. However, if a listeria infection is transmitted to the fetus during pregnancy, it may cause a miscarriage, death of the fetus, or premature birth. The listeriosis may also resolve itself, and your pregnancy can continue.
• Listeriosis can also cause a severe infection in the newborn infant. The infant may develop meningitis days or weeks after birth. The mortality rate in these infant infections is very high; up to half of these newborns die.

The disease’s incubation period varies greatly, also depending upon what symptoms it presents. Symptoms of a gastrointestinal infection may begin already within hours to a few days from transmission. On the other hand, symptoms of a generalized listeria infection may appear only several weeks after transmission. In many cases, a listeria infection presents no symptoms. During pregnancy, listeriosis may present as a mild disease resembling a common cold, but it may also cause back pain, diarrhea, and vomiting. Uterine contractions or sensitivity indicate that the infection has spread to the uterus.

Listeriosis is treated with antibiotics. During pregnancy, medication is usually begun even if listeriosis is only suspected, before the culture results come back. The purpose of early treatment is to prevent the fetus and subsequent newborn infant from being infected.

A listeria infection can be contracted from foods, particularly from unpasteurized dairy products and from vacuum packed and salt-cured fish products. The bacteria can reproduce at refrigerator temperatures and remain alive for years.

• Listeria bacteria die at temperatures of over 70 °C.
• Avoid unpasteurized dairy products, soft cheeses, vacuum packed cold smoked and salt-cured fish products, fish roe, and pateés . If heated to 70 °C or above, however, they are safe to eat.
• Listeria can reproduce at refrigerator temperatures, so always observe the ‘best before’ dates.
• Frozen vegetables must be heated before eating.
• Meat must be thoroughly cooked.
• Raw products must be stored separately from those that are cooked or ready to eat. 

What causes borreliosis, and where in Finland is the risk of infection the highest?

Borreliosis is caused by a bacterium named Borrelia burgdorferi, which may be transmitted to humans via a tick bite. In southern Finland, up to one in three ticks carry this pathogen. Infections are the most common in Åland and in southwestern and southeastern Finland, but cases have been found as far north as Oulu.  

Symptoms of borreliosis

A tick bite generally causes skin changes 0.5 cm to 2 cm in diameter, reddish, raised, and itching. A borrelia infection typically includes a ‘migrating rash’ (erythema migrans), which emerges within days or a few weeks of being bitten. This typically shows as a widening reddish rash more than 5 cm in diameter, where the center often gets lighter in color as the rash spreads. This often disappears within a few weeks but may linger for a month or even longer. 

The skin symptoms may be accompanied by general symptoms of ill health, such as fever, headache, and muscle ache. The rash will heal by itself within weeks or months, but if not treated, the bacteria may remain in the body and cause late manifestations in joints, nerve tissue, or the heart. Up to half of patients in whom the infection is not treated at an early stage develop late manifestations of the disease. 

Borreliosis is the mother’s disease, not the fetus’s

There is no evidence of borreliosis during pregnancy causing damage to the fetus. If you find a tick attached to you, remove it immediately. It is important to monitor the affected skin area for a month for the development of erythema migrans, a spreading rash associated with Lyme disease. If a rash appears around the bite site or you develop other symptoms (such as fever), seek medical evaluation.

Suspected borreliosis, antibiotics and breastfeeding

There are no known cases of a breastfed infant contracting the B. burgdorferi bacterium through breast milk. You can breastfeed normally. The antibiotics used for treatment are safe to use during pregnancy and breastfeeding. 

What causes tick-borne encephalitis, and where in Finland is the risk of infection the highest?

Tick-borne encephalitis (TBE) is caused by a virus that can be transmitted to a human via a tick bite. The virus is transmitted within minutes of the beginning of the tick bite, via the saliva of the tick. There are reports of infections being contracted through unpasteurized milk in the Baltic states and in central Europe. In Finland, ticks carrying the virus are prevalent particularly in Åland and the western archipelago, in Kotka, and in southeastern Finland. 

What are the symptoms of TBE?

Only about one in four of those infected present with symptoms. Fever and a sense of illness usually begin within about a week of being bitten. After the fever, the infection may cause encephalitis, which often does not present symptoms until about a week or more after the fever has subsided. The symptoms of encephalitis include fever, headache, stiffness of the neck, sensitivity to light, and nausea, and in severe cases loss of consciousness and convulsions. Encephalitis always requires hospitalization. 

Can the infection damage the fetus?

It is not known whether the virus could infect the fetus. No effects on the fetus have been reported; the risks of TBE contracted while pregnant have to do with the mother developing a severe form of the disease.  

Is breastfeeding safe?

The mother having TBE does not prevent breastfeeding. The virus will have been in the body for a couple of weeks before symptoms appear, so suspending breastfeeding when symptoms appear will bring no appreciable benefit. Also, there are no known cases of an infant contracting TBE through breast milk.  

TBE can be effectively prevented with vaccination

A TBE vaccine does not contain live pathogens. Giving it to pregnant women who are obliged to stay in a high-risk region for a long period of time may be considered. There is no obstacle to administering a TBE vaccine during breastfeeding. 

The Varizella zoster virus (VZV) belongs to the herpes virus group. It causes chicken pox, which is highly contagious via airborne droplets. The majority of the population have had chicken pox as a child, and this primary infection yields permanent immunity to the disease. Only 1 to 3 in 100 adults (3%) have never had the disease. It has been estimated that between 30 and 50 pregnant women in Finland have the chicken pox each year.  

Chicken pox during pregnancy (maternal varicella) 

If a pregnant woman has chicken pox and the fetus is infected, this may result in a serious case of congenital varicella syndrome, which may lead to the death of the child. The symptoms of congenital varicella syndrome include low birth weight, skin scarring, limb abnormalities, and damage to the central nervous system.  However, the risk of such damage is extremely small. Congenital varicella syndrome is very, very rare, and the majority of fetuses infected with chicken pox do not develop it. 

• The mother having chicken pox during the first trimester of pregnancy causes illness in the fetus in only less than 1% of cases; in other words, fewer than 1 in 100 children delivered by mothers in such a scenario will be affected. Chicken pox is thus not an indication for considering a termination, but the wellbeing of the fetus must be monitored by ultrasound.  
• The risk is the greatest for the fetus in the second trimester (weeks 13 to 24), at which time the risk of birth defects is 2% to 3%, i.e. 2 to 3 out of 100 children delivered by mothers in such a scenario will be affected.  
• If you contract chicken pox after week 24 of your pregnancy, the risk of infection increases significantly: about half of fetuses are infected in such cases. However, it is extremely rare for damage to be caused to the fetus in this scenario. Generally, the fetus will have a mild case of chicken pox with no serious complications or permanent effects.
• The most problematic scenario is one where you contract chicken pox close to childbirth. In this case, the fetus will not be able to derive sufficient protection from your antibodies, and the infant may develop chicken pox after birth. Chicken pox can be life-threatening in a newborn infant. 

The varicella virus is not excreted into breast milk. As long as there are no blisters on your breast, you can breastfeed.  

Symptoms and treatment  

Adult chicken pox may have severe symptoms and may be accompanied by pneumonia requiring intensive care. The incubation period of the virus is 7 to 21 days. The symptoms include a blistery rash beginning on the torso, fever, and headache. 

If you come down with chicken pox while pregnant, or if you have never had chicken pox and come into contact while pregnant with someone who has it, you must have an outpatient consultation with a gynecologist or internal medicine specialist. Any treatment decisions will be made at the hospital on a case-by-case basis.

Erythema infectiosum, also known as ‘fifth disease’, is a viral infection caused by human parvovirus. A maternal fifth disease infection may spread to the fetus and infect the embryonic red blood cells. There is no medication for fifth disease. Once you have had fifth disease, you are immune to it for life.

Fifth disease during pregnancy (maternal erythema infectiosum)

Fifth disease does not cause birth defects, but an infection early in the pregnancy may lead to a miscarriage. If the fetus is infected by the mother’s parvovirus, the parvovirus may destroy red blood cells in the fetus, leading to fetal anemia. Parvovirus may also cause hepatitis and myocarditis in the fetus, leading to generalized edema.  

The risk for the fetus is greatest around weeks 12 to 24, because at that time the fetus’s red blood cell production is at its peak. In most cases, the fetus will heal of its own accord, even if the infection is contracted in early pregnancy. As the infection subsides, the red blood cell count will return to normal. 

An infection in the mother can be diagnosed by a blood test for antibodies. This will reveal whether the mother has had fifth disease at some time in the past. Once you have had fifth disease, you are immune to it for life. The blood test for antibodies will be repeated if necessary a few weeks later.  

Beyond week 24 of the pregnancy, fifth disease rarely presents any problems.

Symptoms and treatment 

Parvovirus is transmitted by droplets and has an incubation period of about 7 days (6 to 16 days). 

Fifth disease is asymptomatic for half of the people who contract it. Typical symptoms include flushed cheeks, rash on the limbs and torso, and joint symptoms. Fifth disease is no longer contagious once the rash emerges. 

If you have had fifth disease in early or middle pregnancy, the status of your fetus will be monitored by ultrasound scans for a period of 12 weeks from contagion. The purpose of the monitoring is to observe whether there are anemia-related changes, such as edema in the fetus. An infection in the fetus may be diagnosed by a sample of amniotic fluid if necessary. The fetus’s hemoglobin may be tested with a blood sample from the umbilical vein, and if it is low, a red blood cell transfusion may be considered. If you are infected with fifth disease beyond week 24 of your pregnancy, there is usually no need to take any action, because fifth disease poses no danger to the fetus late in the pregnancy. 

Prevention 

Parvovirus often causes minor epidemics and is typical among children and adolescents. It is estimated that about 60% of Finns have had fifth disease as a child. It is highly unlikely for the infection to recur. 

Fifth disease is not easily contagious. At-risk groups include pregnant women working with children (staff at day care centers and schools) who have not had fifth disease themselves. Whether they have previously had fifth disease can be confirmed or excluded with a blood test. If a pregnant employee has not had fifth disease, it may be advisable to assign her to different job duties for the duration of the epidemic. 

An enterovirus infection is a typical pediatric disease caused by the enterovirus, most commonly viral type A16. The enterovirus infection occurs as small epidemics, especially in late summer and early autumn. There are several different types of enteroviruses, and symptoms can range from asymptomatic or a mild flu to a more severe clinical picture. In general, the enterovirus infection is a fairly mild disease that resolves on its own in 10 days without sequelae.

The enterovirus infection spreads through droplets, feces and from mother to child, especially during childbirth. The incubation time is 3–6 days. The disease often manifests itself as a febrile illness, accompanied by vesicles and papules in the mouth, and on the hands, feet and other parts of the body. The patient can also experience some throat pain and an upset stomach. As far as is known, the infection does not cause a more severe clinical picture in pregnant women than in non-pregnant women.

An enterovirus infection does not appear to increase the risk of fetal malformations. An infection during pregnancy is treated as a common febrile illness, and when the fever rises above 38 degrees Celsius, it is advisable to lower the fever primarily with paracetamol. There is no targeted drug or vaccine for enterovirus infections. During an enterovirus infection epidemic, it is important to observe careful hand hygiene. However, there is no need to take special precautions even if the mother works in a kindergarten or is at home taking care of a child with an enterovirus infection.

A mother’s enterovirus infection does not prevent breastfeeding the child.

Most of those infected do not present with any symptoms. Possible symptoms include fever, fatigue, sweating, muscle aches, coughing, nausea, and swelling of the lymph nodes in the neck. About 50% to 70% of Finnish women have had a cytomegalovirus infection. As a result, they have antibodies in their system that protect their fetus against infection.

A cytomegalovirus infection may cause serious problems for the fetus. The most dangerous case is if the mother has a primary infection.

• The most dangerous scenario for fetal development is if you contract a cytomegalovirus infection for the first time in your life during pregnancy. The earlier you are in the pregnancy, the more serious the consequences for fetal development will be.  Infections contracted during the first 16 weeks of pregnancy cause the most developmental defects, including fetal growth restriction, central nervous system damage, impaired vision, and impaired hearing.
• It is possible for an earlier infection to be reactivated or for a patient having had the infection to contract the infection again, but in such cases the risk for the fetus is low, and the symptoms are milder. 

About 60 children with fetal cytomegalovirus syndrome are born in Finland every year, and it has been estimated that up to 4% of pregnant women have a CMV infection while pregnant, in most cases symptom-free. 

Good hand hygiene and avoiding bodily fluids are usually considered good enough precautions to prevent infection. Cytomegalovirus is transmitted by contact with mucous membranes, not by skin contact.

Some job duties may involve an elevated risk of infection. The greatest risk of infection is if you are in a job where you are caring for asymptomatic virus carriers and cannot avoid being exposed to patients’ saliva and other bodily fluids. In such a case, please consider reorganizing your work arrangements.

In other animals, toxoplasma inhabits muscle tissue. Humans can be infected by cat feces, by eating uncooked meat, or by eating vegetables with soil adhering, if toxoplasma from cat feces has spread to the soil.

Each year, about 130 mothers are diagnosed with maternal toxoplasmosis infections. About 50 children are born with congenital toxoplasmosis in Finland each year. The risk of this is related to the mother contracting a first-time or primal infection. A primal infection in early pregnancy is the most dangerous for the fetus and may lead to severe complications.  An infection that the mother had earlier poses no danger to the fetus.

The chance of the fetus developing an infection as a result of a primary maternal infection is about 10% in the first trimester, 40% in the second trimester and 70% in the third trimester. The effects of a toxoplasmosis infection for the fetus are the milder the later in the pregnancy the infection occurs. 

Maternal toxoplasmosis may cause a miscarriage, fetus death, premature birth, or congenital toxoplasmosis. Congenital toxoplasmosis in a newborn is a general infection involving inflammation of the central nervous system. 

Most babies born with congenital toxoplasmosis are asymptomatic at birth. Congenital toxoplasmosis can, however, cause problems with hearing and vision, and developmental disorders that emerge later in life. Pharmaceutical treatment during pregnancy and after birth will probably improve the child’s prognosis. 

Toxoplasmosis is often symptom-free and thus can easily remain undiagnosed. Possible symptoms include fever, fatigue, and sweating. The incubation period for the disease is 10 to 14 days on average, and patients recover within a few weeks. 

If you have a toxoplasmosis diagnosis confirmed with laboratory tests, you will be started on medication. The medications used to treat toxoplasmosis are not harmful to the fetus. Medication reduces the risk of the fetus being infected. If the fetus is already infected, medication can improve the newborn’s prognosis. 

If you have a primary infection of toxoplasmosis, we recommend that you observe a withdrawal period of at least 3 to 6 months before getting pregnant.

• Cook meat thoroughly.
• Toxoplasma dies at temperatures over 65 °C. Heating food kills toxoplasma, and it is safe to eat food that has been heated to over 65 °C.   
• Do not touch cat feces with your bare hands. If you empty out a cat’s litter box, wear gloves and wash your hands thoroughly afterwards. The cat litter box should be emptied every day because the toxoplasma oocytes become contagious in 1-5 days.
• Wash vegetables and fruit carefully, and preferably peel them before eating.
• Wash your hands carefully after doing gardening work or after sitting at a playground sandbox. 

Shingles, or Herpes zoster, is a belt-like rash caused by the Varizella zoster or chicken pox virus. Shingles is a consequence of chicken pox that the patient has had earlier. When the patient is ill with chicken pox, the virus travels along nerves to neural nodes. The virus may be reactivated later in life and travel along nerves back to the skin, causing shingles. Shingles blisters contain chicken pox virus. 

Shingles is a local infection but may cause a chicken pox infection in a person who has never had chicken pox if there is direct contact with the shingles blisters. Shingles may cause chronic pain even after the rash subsides. Subject to the physician’s decision, shingles during pregnancy is generally treated with acyclovir. 

• If a mother develops a shingles rash during pregnancy, the mother’s antibodies protect the fetus. Your baby will not be in danger if you contract shingles during pregnancy.
• However, if you have shingles when you give birth, you and your infant should be isolated from other patients.
• When breastfeeding, you must not allow the infant into contact with shingles blisters. 

The Zika virus belongs to the flavivirus group. It generally only causes a mild fever, but it can be very dangerous for the fetus. The Zika virus is endemic in Africa, Southeast Asia and South America. The Zika virus is principally transmitted by mosquitoes that are active in the daytime.

A Zika virus infection during pregnancy may cause microcephalia and other damage to the central nervous system in the fetus. Microcephalia is a condition where the head of the fetus does not grow as large as normal, and this may compromise the development of the brain. In the worst cases, the result may be a severe developmental disability. 

• If you are planning a pregnancy or are already pregnant, you should avoid traveling to regions where the Zika virus is endemic. If you are planning a pregnancy and plan to travel to a high-risk region, you should consult your physician and discuss postponing your pregnancy plans.
• If the travel is essential, please be particularly careful with protection (mosquito repellents, principally those containing DEET; protective clothing; insecticides; netting).
• Always check the incidence of Zika virus before planning travel to a potential risk area (ECDC).
• The Zika virus may be transmitted via semen. The male partner of a woman who is pregnant or who is planning a pregnancy should use a condom for the remainder of the pregnancy if he has visited an endemic Zika virus region, and for at least 3 months before the planned pregnancy. The withdrawal period for the man goes up to 6 months if he has had an actual or suspected Zika virus infection. 

For more information on the Zika virus, visit the website of the Finnish Institute for Health and Welfare. 

Please avoid travel to malaria regions during pregnancy, because pregnant women have a high risk of contracting a severe form of malaria. During pregnancy, particularly early and towards the middle, the risk of contracting malaria is 2 to 3 higher than for non-pregnant women. 

Malaria can cause severe anemia in a pregnant woman. Malaria elevates the risk of miscarriage, arrested development, low weight, premature birth, and fetal death. Also, a malaria infection during pregnancy may cause premature separation of the placenta and elevates the risk of pre-eclampsia. The newborn infant may develop congenital malaria as a result of the mother having malaria during pregnancy.

Prevention 

Prophylactic medications do not yield complete protection, and wearing protective clothing is therefore essential. Mosquito nets and repellents must also be used. The choice of prophylactic medication must be based on the sensitivity of the local malaria strain to medication and recommendations concerning the area in question. Any risks related to the stage of the pregnancy and the medication must be taken into account when planning the prophylaxis.  

• Chloroquine and chloroquine-proguanil combinations are safe, but nowadays they are only effective in a small number of areas.  
• Mefloquine can be used for malaria prophylaxis throughout pregnancy if visiting a malaria area with chloroquine-resistant malaria cannot be avoided (THL 2023).
• Doxycycline may be used in early pregnancy (up to week 14) if there are weighty reasons for doing so (THL 2023). From week 14, this medication must not be used.  
• The atovaquone-proguanil combination is not recommended during pregnancy, because there is little information on its use as a prophylactic in this context. If there are no other alternatives (if mefloquine use is contraindicated) and travel to a high-risk malaria region cannot be avoided, this medication may be permissible (THL 2023). 

For more information on prophylactic medication, see the health guide for travelers edited by the Finnish Institute for Health and Welfare. This guide also contains general information on malaria and how to protect against it.

Symptoms and treatment 

Malaria generally has a incubation period of 7 to 30 days but can take months or even years to emerge. Prophylactic medication may extend the incubation period. 

Typical symptoms include repeated bouts of fever beginning with chills, and sweating as the fever breaks. Initially, the fever may be continuous and may be accompanied by stomach symptoms, severe diarrhea, respiratory symptoms, and central nervous system symptoms such as disorientation and reduced consciousness.

If you develop a fever after a trip to a malaria region, see a doctor. Malaria can be diagnosed from a blood sample taken from a fingertip, and the test results are ready in a few hours. Malaria treatment must be begun immediately.