Infections in Pregnancy


Rubella is also known as German measlesCongenital rubella syndrome is caused by maternal infection with the rubella virus during the first 20 weeks of pregnancy. The risk is highest before ten weeks gestation.

Women planning to become pregnant should ensure they have had the MMR vaccine. When in doubt, they can be tested for rubella immunity. If they do not have antibodies to rubella, they can be vaccinated with two doses of the MMR, three months apart.

Pregnant women should not receive the MMR vaccination, as this is a live vaccine. Non-immune women should be offered the vaccine after giving birth.

The features of congenital rubella syndrome to be aware of are:

  • Congenital deafness
  • Congenital cataracts
  • Congenital heart disease (PDA and pulmonary stenosis)
  • Learning disability



Chickenpox is caused by the varicella zoster virus (VZV). It is dangerous in pregnancy because it can lead to:

  • More severe cases in the mother, such as varicella pneumonitishepatitis or encephalitis
  • Fetal varicella syndrome
  • Severe neonatal varicella infection (if infected around delivery)


Mothers that have previously had chickenpox are immune and safe. When in doubt, IgG levels for VZV can be tested. A positive IgG for VZV indicates immunity. Women that are not immune to varicella may be offered the varicella vaccine before or after pregnancy.

Exposure to chickenpox in pregnancy:

  • When the pregnant woman has previously had chickenpox, they are safe
  • When they are not sure about their immunity, test the VZV IgG levels. If positive, they are safe.
  • When they are not immune, they can be treated with IV varicella immunoglobulins as prophylaxis against developing chickenpox. This should be given within ten days of exposure.


When the chickenpox rash starts in pregnancy, they may be treated with oral aciclovir if they present within 24 hours and are more than 20 weeks gestation.

Congenital varicella syndrome occurs in around 1% of cases of chickenpox in pregnancy. It occurs when infection occurs in the first 28 weeks of gestation. The typical features include:

  • Fetal growth restriction
  • Microcephaly, hydrocephalus and learning disability
  • Scars and significant skin changes located in specific dermatomes
  • Limb hypoplasia (underdeveloped limbs)
  • Cataracts and inflammation in the eye (chorioretinitis)



Listeria is an infectious gram-positive bacteria that causes listeriosis. Listeriosis is many times more likely in pregnant women compared with non-pregnant individuals. Infection in the mother may be asymptomatic, cause a flu-like illness, or less commonly cause pneumonia or meningoencephalitis.

Listeriosis in pregnant women has a high rate of miscarriage or fetal death. It can also cause severe neonatal infection.

Listeria is typically transmitted by unpasteurised dairy productsprocessed meats and contaminated foods. Pregnant women are advised to avoid high-risk foods (e.g. blue cheese) and practice good food hygiene.


Congenital Cytomegalovirus

Congenital cytomegalovirus infection occurs due to a cytomegalovirus (CMV) infection in the mother during pregnancy. The virus is mostly spread via the infected saliva or urine of asymptomatic children. Most cases of CMV in pregnancy do not cause congenital CMV.

The features of congenital CMV are:

  • Fetal growth restriction
  • Microcephaly
  • Hearing loss
  • Vision loss
  • Learning disability
  • Seizures


Congenital Toxoplasmosis

Infection with the Toxoplasma gondii parasite is usually asymptomatic. It is primarily spread by contamination with faeces from a cat that is a host of the parasite. When infection occurs during pregnancy, it can lead to congenital toxoplasmosis. The risk is higher later in the pregnancy.

There is a classic triad of features in congenital toxoplasmosis:

  • Intracranial calcification
  • Hydrocephalus
  • Chorioretinitis (inflammation of the choroid and retina in the eye)


Parvovirus B19

Parvovirus B19 infection typically affects children. It is also known as fifth diseaseslapped cheek syndrome and  erythema infectiosum. It is caused by the parvovirus B19 virus. The illness is self-limiting, and the rash and symptoms usually fade over 1 – 2 weeks.

Parvovirus infection starts with non-specific viral symptoms. After 2 – 5 days, the rash appears quite rapidly as a diffuse bright red rash on both cheeks, as though they have “slapped cheeks”. A few days later a reticular mildly erythematous rash affecting the trunk and limbs appears, which can be raised and itchy. Reticular means net-like.

Healthy children and adults have a low risk of any complications, and management is supportive. They are infectious 7 – 10 days before the rash appears. They are not infectious once the rash has appeared. Significant exposure to parvovirus is classed as 15 minutes in the same room, or face-to-face contact, with someone that has the virus.

Infections with parvovirus B19 in pregnancy can lead to several complications, particularly in the first and second trimesters. Complications are:

  • Miscarriage or fetal death
  • Severe fetal anaemia
  • Hydrops fetalis (fetal heart failure)
  • Maternal pre-eclampsia-like syndrome


Fetal anaemia is caused by parvovirus infection of the erythroid progenitor cells in the fetal bone marrow and liver. These cells produce red blood cells, and the infection causes them to produce faulty red blood cells that have a shorter life span. Less red blood cells results in anaemia. This anaemia leads to heart failure, referred to as hydrops fetalis.

Maternal pre-eclampsia-like syndrome is also known as mirror syndrome. It can be a rare complication of severe fetal heart failure (hydrops fetalis). It involves a triad of hydrops fetalis, placental oedema and oedema in the mother. It also features hypertension and proteinuria.

Women suspected of parvovirus infection need tests for:

  • IgM to parvovirus, which tests for acute infection within the past four weeks
  • IgG to parvovirus, which tests for long term immunity to the virus after a previous infection
  • Rubella antibodies (as a differential diagnosis)


Treatment is supportive. Women with parvovirus B19 infection need a referral to fetal medicine to monitor for complications and malformations.


Zika Virus 

The zika virus is spread by host Aedes mosquitos in areas of the world where the virus is prevalent. It can also be spread by sex with someone infected with the virus. It can cause no symptoms, minimal symptoms, or a mild flu-like illness. In pregnancy, it can lead to congenital Zika syndrome, which involves:

  • Microcephaly
  • Fetal growth restriction
  • Other intracranial abnormalities, such as ventriculomegaly and cerebellar atrophy


Pregnant women that may have contracted the Zika virus should be tested with viral PCR and antibodies to the Zika virus. Women with a positive result should be referred to fetal medicine for close monitoring of the pregnancy. There is no treatment for the virus.


Last updated September 2020
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