Recognising and treating infectious illnesses in pregnancy

Pregnant women and people may be more susceptible to being affected by infectious illnesses. However, an individual’s immune system may respond differently depending on the infection and the stage of pregnancy (Mor et al, 2010).

Chicken pox

Chicken pox is a very infectious illness which causes a fever and a rash. Most women and birthing parents (9 out of 10) are immune to chicken pox. This is because they have had it previously, usually in childhood, and their body has produced antibodies (RCOG, 2024).

Because of this, getting chicken pox when pregnant is uncommon. Only 3 in 1000 people will get chicken pox, meaning 997 in 1000 won’t (RCOG, 2024).

Getting chicken pox in pregnancy can lead to the mother or birthing person experiencing (RCOG, 2024):

• chest infections (pneumonia)
• inflammation of the liver (hepatitis)
• inflammation of the brain (encephalitis) 

Very rarely, it can lead to death.

What are the risks for the baby? (RCOG, 2024)

The risk for the baby increases the further along in pregnancy that chicken pox is caught. If caught up to 24 weeks, the risks are low. The risk of the baby getting chicken pox is highest from 36 weeks of pregnancy.  

If the mother or birthing parent gets chicken pox at this time, there is a 1 in 4 chance the baby will too.

If the mother or birthing parent hasn’t had chicken pox before, they should (RCOG, 2024): 

• Go to the GP as soon as possible, to have a blood test to see if they are immune (8 out of 10 will be)
• Contact the GP if they develop a rash. Antiviral tablets can be given if a blood test shows they are not immune. 

Colds and Flu  

It’s common to get a cold during pregnancy and they can be hard to avoid. Colds can be treated with self-care and paracetamol (UKTIS, 2024). Washing hands frequently and catching sneezes with a tissue can stop them spreading (UKTIS, 2024).

Flu and pregnancy

Pregnant women and people are at a higher risk of flu complications, because of changes to the immune system and lungs during pregnancy. They are more likely to get complications such as pneumonia and need to go to hospital.  

A GP can prescribe antivirals if necessary, so get medical help if flu is suspected (UKTIS, 2024).

Pregnant women and people are offered the flu vaccination because of the higher risk of complications (UKTIS, 2024). They can have this at any stage of pregnancy.

Covid-19

Pregnant women and people are at a higher risk of getting seriously ill from Covid-19. It can also put the baby at risk if caught in the third trimester (NHS, 2022).

The COVID-19 vaccination is an effective way to protect both the mother and baby against the virus (NHS, 2022).

Mild symptoms of COVID-19 can be soothed by rest and drinking plenty of fluids.

Cytomegalovirus (CMV)

Cytomegalovirus (CMV) is a common virus that is usually harmless. Most people don’t realise they have it, however women and pregnant people can pass it onto their baby.  

It is the most common viral infection in newborn babies and is more serious for them. It is estimated to affect 1 in 200 babies born in the UK (NHS, 2023; RCOG, 2024).

If a baby is born with a CMV infection, it is called congenital CMV (Action Medical Research, 2024). They might have (NHS, 2023):

• a rash
• jaundice
• a low birth weight
• hearing problems
• problems with the eyes
• a smaller head than usual (microcephaly)
• problems with the liver and spleen
• cerebal palsy 

Babies born with CMV will have tests to check their liver, kidneys, brain, eyes and hearing (NHS, 2023). Follow up tests should be done at two years of age to check their hearing and brain development (RCOG, 2024).

CMV is the leading cause of non-genetical child hearing loss (Action Medical Research, 2024).

Is it possible to reduce the risk of getting CMV?

Pregnant women or people who work closely with children or already have a young family have a higher chance of getting CMV (NHS, 2023).

The best way to reduce the chance of getting CMV in pregnancy is to (NHS, 2023):

• follow good hygiene practices such as washing hands regularly (especially if looking after young children)
• avoid sharing food, cutlery and drinking glasses
• not kiss young children on the lips  

Diarrhoea and vomiting

Although unpleasant, diarrhoea and vomiting can usually be treated at home (NHS, 2023).

Help get better by (NHS, 2023):

• Drinking plenty of fluids like water or squash
• Staying at home and resting
• Eating if you feel you can 

A recent study found that occasionally norovirus (a stomach bug which causes vomiting and diarrhoea) may lead to premature birth if contracted in the last few weeks of pregnancy (Cao et al, 2024).  

The pregnant woman or person should see the GP at any stage of pregnancy if (Tommy’s, 2023):

• They can’t keep any fluids down  
• The vomiting and diarrhoea doesn’t go away within 48 hours 

Genital herpes

Genital herpes is a sexually transmitted infection that can cause small blisters around the genitals, anus, bottom or thighs. These blisters burst to leave red, open sores (NHS, 2023).

Signs of genital herpes include (NHS, 2023):

• Pain when having a pee
• Tingling, burning or itching around the genitals
• Unusual discharge 

It is caused by a virus called herpes simplex, that stays in the body and can break out again.  

Neonatal herpes

If the baby contracts the herpes simplex virus, they can develop neonatal herpes. This can be serious and sadly sometimes fatal, although most babies recover with treatment. It can happen if (NHS, 2023):

• an outbreak happens when the woman or pregnant person is giving birth
• the woman or pregnant person gets genital herpes for the first time 

In this case, the mother or pregnant parent will be given medicine from 32 weeks (NHS, 2023).

Vaginal birth is often possible. However, because of risk of transmission, caesarean birth might be offered (NHS, 2023). 

Group B Strep (GBS)

Group B Strep is a common kind of bacteria called streptococcal bacteria, which can be found in the bottom or vagina. It is one of many bacteria that lives in our body and doesn’t normally cause a problem. Most people won’t realise they have it (Group B Strep Support, 2025; NHS, 2024).

However when pregnant, there is a small risk that it could spread to the baby during labour and make them ill. This happens in about 1 in 1,750 pregnancies (NHS, 2024).

There is also an extremely small risk that the pregnant woman or person might miscarry the baby (NHS, 2024).

It’s not usually tested for in pregnancy as it is so common, however it may be found during a vaginal swab or urine test for something else. It is also possible to pay for a private test (Group B Strep Support, 2025; NHS, 2024).

If Group B Strep is found in the pregnant woman or person, or they have had a baby affected by GBS before, they may need extra treatment and looking after. The advice may be to (NHS, 2024):

• Contact the midwife as soon as the waters break or labour starts
• Be given antibiotics into a vein during labour
• Stay in hospital for 12 hours after giving birth 

The baby will be monitored in after birth for up to 12 hours, and will be given antibiotics if they develop symptoms (NHS, 2024). 

Pyelonephritis

Pyelonephritis is a type of urinary tract infection (UTI) that affects the kidneys. It is one of the most common conditions requiring hospitalisation among pregnant women and people (Gomi et al, 2015).

Symptoms of pyelonephritis include:

• fever
• feeling sick
• vomiting
• pain in the side of the body 

Severe pyelonephritis may be treated with intravenous antibiotics (antibiotics given into the vein) in hospital. Any symptoms should be reported to a midwife or GP for swift treatment if necessary (Gomi et al, 2015).

Sepsis  

Sepsis is a serious condition where the body’s response to infection causes it to attack its own organs and tissues. Read our article on maternal sepsis. 

Thrush

Thrush is a yeast infection, which is caused by the Candida fungus. For some people, it is always present in the vagina but it is kept under control by normal bacteria (NHS, 2024).

During pregnancy, and especially in the third trimester, changes in the body might cause thrush. It’s not thought to harm the baby (NHS, 2024).

Thrush can cause (NHS, 2024):

• itching and irritation around the vulva and vagina
• white discharge that doesn’t smell
• soreness and stinging when having a pee or during sex
• redness around the vagina (which can be hard to see on darker skin tones) 

Thrush can be treated by putting an anti-fungal cream on the area, or putting a tablet into the vagina which contains the anti-fungal medicine (NHS, 2024).  

Speak to a doctor or midwife before any treatment for thrush while pregnant (NHS, 2024). Anti-fungal tablets taken by mouth shouldn’t be used during pregnancy. 

Toxoplasmosis

Toxoplasmosis is a common infection caused by the parasite Toxoplasma gondii, which lives mainly in cats. However, it can infect humans and other animals (Tommy’s, 2024).

The infection is not usually serious, but it can cause problems in pregnancy. A toxoplasmosis infection can cause miscarriage. If the infection spreads to the baby, it can cause serious health problems (NHS, 2023).

To avoid getting the infection in pregnancy, women and birthing parents are recommended to (NHS, 2023):

• wear gloves while gardening
• wash hands before preparing food and eating
• wash fruit and vegetables thoroughly
• cook meat thoroughly
• avoid cat poo in cat litter
• avoid pregnant sheep or lambs 

Toxoplasmosis cannot be caught from stroking a cat, or having a cat as a pet (NHS, 2023).

It is also important to avoid eating:

• raw or undercooked meat
• cured meats like salami
• unpasteurised goat’s milk 

Speak to your GP or midwife and ask them for a blood test if you are worried that you may have picked up a toxoplasmosis infection. An infection can be treated with antibiotics (Tommy’s, 2024).

Urinary tract infection (UTI)

Urinary tract infections (UTIs) are common during pregnancy. A mild UTI can often be treated with self-care measures such as taking paracetamol and drinking lots of fluids. Over the counter treatments for UTIs are not recommended during pregnancy (NICE, 2025).

If symptoms don’t improve or get worse, antibiotics may be required. These are very effective in treating UTIs (Vasquez et al, 2011).

Untreated UTIs can lead to (Vasquez et al, 2011):

• early labour
• premature breaking of the waters
• sepsis for mother and baby 

If a pregnant woman has recurrent UTIs, they should be referred to an obstetrician for further tests and follow-up (NICE, 2025).

Zika virus

Zika virus is mainly spread by mosquitoes and is found in some parts of the world. The type of mosquitos that carry the virus are not found in the UK (NHS, 2022).

Zika virus can harm the developing baby’s brain, so pregnant women and parents should postpone travel to areas where the virus might be present until after the baby is born (NHS, 2022; RCOG, 2019).  

Before travelling while pregnant, it is important to check whether there are any risks for the country to be visited (NHS, 2022).

If travelling in an area with a risk of Zika virus:

• use insect repellent that is 50% DEET based
• wear loose clothing that covers arms and legs
• sleep under a mosquito net treated with insecticide