Infections in pregnancy

Most germs are normally harmless, but when trying for a baby, or newly pregnant, you may be more at risk. Some illnesses may be able to affect your growing baby

Common viral infections

German measles (Rubella) in pregnancy

Catching rubella during pregnancy can be very dangerous for the developing baby, particularly in the first 16 weeks. Complications can include brain damage, heart defects, deafness or eye problems as well as possible miscarriage.

You should have a simple blood test before you start trying for a baby to check if you are immune to rubella.

Chickenpox (Varicella)

If you are not immune and catch chickenpox in the first 20 weeks of your pregnancy while the embryo is still forming, it can cause a range of abnormalities.

If the infection is caught between 20 and 36 weeks the baby is unlikely to have any problems but may develop shingles in the first few years of its life. After 36 weeks the baby may develop chickenpox in the womb, which may be more serious.

Slapped Cheek disease (Parvovirus B19)

Around 60% of adults are already immune to this virus. Fortunately, if you catch this infection in pregnancy there is only a small chance of it affecting the baby.

If it is caught in the first 20 weeks of pregnancy it slightly increases the risk of miscarriage and a condition that can cause heart problems. There is no evidence that infection with parvovirus B19 during pregnancy causes birth defects or development problems later in childhood.

Sexually transmitted infections

If you are thinking of starting a family, it might be a good time to talk honestly to your partner about your previous sexual histories. A one night stand in the past may have resulted in an STI that isn’t apparent due to the lack of symptoms.

It can be a good idea for both partners to have a sexual health check up before trying for a baby. The best places to go are a genito-urinary medicine (GUM) clinic, sexual health clinic, your own doctor or a young people’s clinic.

All information given will remain confidential, and screening for specific infections only takes place with consent.

You can find details of local genito-urinary medicine (GUM) clinics by contacting the Sexual Health Line on 0800 567 123 or the Family Planning Association on or 0845 122 8690.


Toxoplasmosis is a tiny parasite that is found in infected meat, cat’s faeces, soil that cats have dirtied, as well as unpasteurised goat’s milk and products made from it. If it is caught for the first time in pregnancy the effects of toxoplasmosis can affect the unborn baby.

If you get toxoplasmosis in the early stages of pregnancy, the risk of miscarriage is increased. It’s rare for the infection to pass to the baby during early pregnancy, but if it does, it can cause serious health problems. In later pregnancy, the infection more commonly passes to the baby.

However, babies infected during later pregnancy are less likely to develop serious health problems. Risks for the infected fetus include brain abnormalities, developmental delay and eye disease.

Find out more about Toxoplasmosis.


Cytomegalovirus (CMV) is a usually harmful virus that can infect anyone - adults or children. Most people who catch it will have no signs or symptoms and no long-term effects. It can cause long-term problems for babies who become infected in the womb however. This is known as congenital CMV infection. 

Find out more about cytomegalovirus

Find out more in our Conception FAQs

Pregnancy in the news


  1. J David, Steer P et al (2010) High risk pregnancy, management options, Elsevier Saunders
  2. BMJ Best Practice (accessed March 2014)
  3. Sangkomkamhang US, Lumbiganon P, Prasertcharoensook W, Laopaiboon M (2009)Antenatal lower genital tract infection screening and treatment programs for preventing preterm delivery, The Cochrane Collaboration, Wiley
  4. RCOG (2011) When your waters break early (preterm prelabour rupture of membranes) – information for you, Royal College of Obstetricians
  5. Rennie JM (2012), Rennie and Robertons Textbook of Neonatology, Fifth edition. Elsevier.
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Last reviewed on April 1st, 2014. Next review date April 1st, 2017.

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