Pregnancy and baby

Infections in pregnancy that may affect your baby

Am I or my unborn baby at risk of parvovirus?

Media last reviewed: 07/03/2013

Next review due: 07/03/2015

Throughout life, we all come into contact with many viruses and bacteria. As part of our defence mechanism, the body makes antibodies to help fight infection. If you have antibodies against a particular virus or bacteria, you are 'immune' and the antibodies help prevent or reduce the impact of getting the infection again.  

Rubella in pregnancy

If you catch rubella (German measles) in the first four months of pregnancy it can seriously affect your baby's sight and hearing, as well as causing brain and heart defects. All children are now offered a vaccine against rubella through the MMR immunisation when they are 13 months old and a second immunisation before they start school.

If you are not immune and you do come into contact with rubella, tell your doctor at once. Blood tests will show whether you have been infected and you'll be able to decide what action to take.

Sexually transmitted infections in pregnancy

Sexually transmitted infections (STIs) are on the increase and chlamydia is the most common. STIs often have no symptoms, so you may not know if you have one. However, many STIs can affect your baby’s health during pregnancy and after the birth.

If you have any reason to believe that you or your partner may have an STI, go for a check-up as soon as possible. You can ask your GP or midwife or, if you prefer, go to a genitourinary medicine (GUM) clinic or sexual health clinic. Your confidentiality is guaranteed. Find a sexual health service near you, including GUM or sexual health clinics.

If you're under 25 years old, you can also visit a Brook centre for free, confidential advice, or you can contact the National Chlamydia Screening Programme for a free, confidential test. You may also be able to order a free chlamydia test online.  

HIV and AIDS in pregnancy

You'll be offered a confidential HIV test as part of your routine antenatal care. Your midwife or doctor will discuss the test with you, and counselling will be available if the result is positive. Find out about coping with a positive HIV test. You can also go to a sexual health clinic for an HIV test and advice.

Current evidence suggests that an HIV-positive mother in good health and without symptoms of the infection is unlikely to be adversely affected by pregnancy. HIV-positive mothers can pass on the virus through breastmilk. However, it's possible to reduce the risk of transmitting HIV to your baby during pregnancy and after birth. The page on antenatal checks and tests has more information about these risks. 

If you're HIV-positive, talk to your doctor or midwife about your own health and the options open to you, or contact organisations such as Positively UK or the Terrence Higgins Trust for information and support. The Royal College of Obstetricians and Gynaecologists has more information on HIV and pregnancy.  

Hepatitis B in pregnancy

Hepatitis B is a virus that infects the liver. Many people with hepatitis B will show no sign of illness, but can be carriers and may infect others. The virus is spread by having sex with an infected person without using a condom, and by direct contact with infected blood. If you have hepatitis B or are infected during pregnancy, you can pass the infection on to your baby at birth.

All pregnant women are offered a blood test for hepatitis B as part of their antenatal care. Babies who are at risk should be given the hepatitis B vaccine at birth to prevent infection and serious liver disease later on in life. Immunisation at birth is 90-95% effective in preventing babies developing long-term hepatitis B infection. The first dose is given within 24 hours of birth. Two more doses are given at one and two months, with a booster dose at 12 months. A few babies may also need an injection of antibodies called immunoglobulin soon after birth.

Your baby will be tested for hepatitis B infection at 12 months. Any babies who have become infected should be referred for specialist assessment and follow up.  

Hepatitis C in pregnancy

Hepatitis C is a virus that infects the liver. Many people with hepatitis C have no symptoms and are unaware they're infected. The virus is transmitted by direct contact with infected blood. In people who take illegal drugs, this can be as a result of sharing blood-contaminated needles and drug-injecting equipment. People who received a blood transfusion in the UK prior to September 1991 or blood products prior to 1986 may also be at risk.

Hepatitis C can also be transmitted by receiving medical or dental treatment in countries where hepatitis C is common and infection control may be poor; or by having sex with an infected partner.

If you have hepatitis C, you may pass the infection on to your baby, although the risk is much lower than with hepatitis B or HIV. This cannot currently be prevented. Your baby can be tested for hepatitis C and, if your baby is infected, he or she can be referred for specialist assessment.

Herpes in pregnancy

Genital herpes infection can be dangerous for a newborn baby. Genital herpes can be caught through genital contact with an infected person or from oral sex with someone who has cold sores (oral herpes). Initial infection causes painful blisters or ulcers on the genitals. Less severe attacks usually occur for some years afterwards.

If you or your partner have herpes, use condoms or avoid sex during an attack. Avoid oral sex if you or your partner have cold sores or genital sores (active genital herpes). Tell your doctor or midwife if either you or your partner have recurring herpes or develop the symptoms described above.

If your first infection occurs in pregnancy, treatment is available. If your first infection occurs near the end of pregnancy or during labour, a caesarean section may be recommended to reduce the risk of passing herpes to your baby.

Chickenpox in pregnancy

Chickenpox infection in pregnancy can be dangerous for both mother and baby, so if you think you may have chickenpox it's important to seek advice early.

Around 95% of women are immune to chickenpox. But, if you've never had chickenpox (or you're unsure if you've have it) and you come into contact with a child or adult who has it, speak to your GP, obstetrician or midwife immediately. A blood test will establish if you are immune.

Find out more about the complications of chickenpox for you and your unborn baby and watch this video explaining what to do if you're exposed to chickenpox in pregnancy.

Toxoplasmosis in pregnancy

You can catch toxoplasmosis through contact with cat faeces. If you are pregnant, the infection can damage your baby, so take precautions (see Infections transmitted by animals, further down this page, or preventing toxoplasmosis). Most women have had the infection before pregnancy and will be immune.

If you feel you may have been at risk, discuss it with your GP, midwife or obstetrician. If you are infected while you're pregnant, treatment for toxoplasmosis is available. Treatment can reduce the risk of the baby becoming infected. Where the baby is infected, treatment may reduce the risk of damage.

Parvovirus B19 (slapped cheek disease) in pregnancy

Parvovirus B19 infection is common in children and causes a characteristic red rash on the face, so it's often called slapped cheek disease.

Although 60% of women are immune to this infection, parvovirus is highly infectious and can be harmful to the baby. If you come into contact with anyone who is infected you should talk to your doctor, who can check whether you are immune through a blood test. In most cases, the baby is not affected when a pregnant woman is infected with parvovirus.

Group B streptococcus in pregnancy

Group B streptococcus (GBS, or group B strep) is a bacteria carried by up to 30% of people but it rarely causes harm or symptoms. In women it's found in the intestine and vagina and causes no problem in most pregnancies. In a small number of pregnancies, it infects the baby, usually just before or during labour, leading to serious illness.

If you've already had a baby who had a GBS infection, you should be offered antibiotics during labour to reduce the chances of your new baby getting the infection. If you have had a group B streptococcal urinary tract infection with GBS (cystitis) during the pregnancy, you should also be offered antibiotics in labour.

GBS infection of the baby is more likely to occur if:

  • your labour is premature (before 37 weeks of pregnancy)
  • your waters break early
  • you have a fever during labour
  • you currently carry GBS

Your midwife or doctor will assess whether you need antibiotics during labour to protect your baby from being infected.

It's possible to be tested for GBS late in pregnancy, if you have concerns talk to your doctor or midwife. 

Cytomegalovirus (CMV) in pregnancy

Cytomegalovirus (CMV) is a common virus that is one of the herpes group of viruses, which can also cause cold sores. Infection can be hazardous during pregnancy as it can cause problems for unborn babies. This is particularly true if a pregnant woman has had no previous exposure to CMV before becoming pregnant (in other words, she is not immune).

Find out more about:

Infections transmitted by animals


Cat faeces may contain toxoplasma, an organism that causes toxoplasmosis infection. Toxoplasmosis can damage your baby. To reduce the risk of infection:

  • avoid emptying cat litter trays while you’re pregnant
  • if nobody else can empty the litter tray, use disposable rubber gloves – trays should be cleaned daily and filled with boiling water for five minutes
  • avoid close contact with sick cats
  • wear gloves when gardening (even if you don’t have a cat) in case the soil is contaminated with faeces
  • wash your hands and gloves after gardening
  • if you do come into contact with cat faeces, wash your hands thoroughly
  • follow general food hygiene rules, see how to prepare food safely and how to store food safely


Lambs and sheep can carry an organism called Chlamydia psittaci, which is known to cause miscarriage in ewes. They also carry toxoplasma. Avoid lambing or milking ewes and all contact with newborn lambs. If you experience flu-like symptoms after coming into contact with sheep, tell your doctor.


Research is on-going to see if pigs can be a source of hepatitis E infection. This infection is dangerous in pregnant women, so avoid contact with pigs and pig faeces. There is no risk of hepatitis E from eating cooked pork products.

Page last reviewed: 07/02/2013

Next review due: 07/02/2015


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The 2 comments posted are personal views. Any information they give has not been checked and may not be accurate.

MandaP said on 08 August 2011

there's information on CMV in the common questions section on pregnancy:

But why it's not included on this page or even linked to it is a mystery, hopefully it'll be rectified

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Lori1977 said on 22 May 2011

What about CMV this is a virus that affects most people in their life but if caught during pregnancy can be passed onto the featus and cause numerous disabilities and in some cases death, why are we not warned about this when we become pregnant or inform our GPs that we are trying for a baby?

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Media last reviewed: 20/08/2013

Next review due: 20/08/2015