Tests for infections and illnesses when you’re pregnant

Certain illnesses or infections contracted during pregnancy could impact the health of your baby. Read our guide to see if you need to get tested


No matter how much you take care of your health during pregnancy, you may catch an illness or infection that could be harmful to your baby, such as a childhood disease like chickenpox or an infection like strep throat.


As a general rule of thumb, independent midwife Pam Wild advises, “If you are worried you have come into contact with someone who is unwell, do speak to your doctor or midwife straight away. And if your GP then decides you need antibiotics or other medicines to treat an illness or infection during your pregnancy, do trust them and try not to worry.” She adds, “We are so much more aware these days about what drugs can safely be given to pregnant women, and the testing of them is so much more robust. And your doctor will always double check that anything he is prescribing is safe for mums-to-be.”

Here’s a few of the more common illnesses to be aware of – ones where you might need tests or treatment when you’re expecting.


It is actually really rare to get chickenpox when you are pregnant –  it’s estimated that only 3 in 1,000 women (that’s 0.003%) will get it during pregnancy. Symptoms include mild flu-like symptoms and a spotty, blistering rash.

Who might need the test? If you’ve had chickenpox before, you will most likely be immune but if you haven’t had it or aren’t sure – and you’ve come into contact with someone with chickenpox – then see your doctor or midwife straight away.

What does the test involve? A simple blood test can show if you have antibodies to the chickenpox virus. If you do, then you’ve already had it. If you don’t, then you could be at risk and may be offered an immunoglobulin injection, which contains the antibodies. If you do end up catching chickenpox, your GP may prescribe aciclovir – an antiviral medicine which doesn’t stop or cure the pox – but can reduce symptoms.

What’s the risk to my baby?

Complications are pretty rare, and the NHS line is reassuring – they say that “most pregnant women who get chickenpox recover, with no adverse effects for the baby”. The very small risks that are associated with it vary depending on how far into your pregnancy you are, and include foetal varicella syndrome (FVS) which can affect baby’s skin, eyes, legs, arms, brain, bladder or bowel. If you get chickenpox late in your pregnancy –  between 28 and 36 weeks, the virus stays in the baby’s body but without symptoms, although it could come out in the first couple of years as shingles.

What mums on our forums are saying… 

“My son has just had chicken pox and i am 15 weeks pregnant. I have had them and my doc said not too worry unless you are in early stages. The midwife also told me it was fine as if you are immune then the baby is too.” – bobbysmum

Strep B (GBS)

Strep B (group B streptococcus or GBS) has no obvious symptoms and is carried by up to 30% of people. It is usually found in the intestine or vagina, and ‘colonises’ the vagina in roughly 22% of all women. It’s important to note that most women who carry it have healthy babies. However, strep B can be passed to your baby during childbirth leading to early onset GBS. While rare, in some instances, it can be life-threatening for your newborn if not detected.

Who might need the test?

There is a test for Strep B (ECM), but it’s not routinely used in pregnancy. You are more likely to find out you have Strep B after having a vaginal swab for something else. Strep B can also come and go, so testing at one point does not mean you won’t have it later. However, if you have additional risk factors that increase your chances of getting GBS or your newborn getting it, e.g. if you’ve previously had a baby who was born with GBS, you’ll be offered intravenous antibiotics when you go into labour (or when your waters break) to reduce the risk of your new baby picking it up during delivery. You should also be offered them if you’ve had a urinary tract infection with GBS (such as cystitis) during your pregnancy.

What does the test involve? Speak to your midwife or doctor about testing, as although it is possible late in pregnancy, it is not routine.

What’s the risk to my baby?

Approximately one in 2,000 babies develops a GBS infection shortly after birth, and for around one in 10, it will be fatal, but it is extremely rare for a baby not to recover from a Strep B infection.

What mums on our forums are saying… 

“I had strep B and had never heard of it before. We discovered it by chance as I thought I was going into labour and a test then came back positive. I was really worried as I found out it can lead to  meningitis, but they gave me antibiotics and when my baby was born she was fine. Apparently Strep B is really common in pregnancy.” –kamaria 

For more information on strep B in pregnancy, visit: Group B Strep Support.


Slapped cheek disease (Parvovirus B19 or fifth disease)

Slapped cheek is a common childhood virus often affecting nursery-age kids. The main symptom is a red rash on the face but symptoms can also include a headache, mild fever and sore throat. However, in about 20-30% of infections, there are no symptoms and by the time the rash appears, the person is no longer contagious. It’s thought around 60% of adults are immune, having had it as children.

Who might need the test? Anyone who is not immune and who has come into contact with someone with the virus but as it is highly infectious, you should have your immunity checked by your midwife or GP. Adult symptoms include rash, high temperature and joint pain.

What does the test involve? A simple blood test.

What’s the risk to my baby?

According to the NHS, your baby is unlikely to be affected if you get slapped cheek syndrome during pregnancy. However, if you contract it between 9-20 weeks of pregnancy, there’s an increased risk of miscarriage because it can cause unborn babies to develop severe anaemia (the CDC states the risk is less than 5% in all pregnant women). There’s also a small risk of your baby developing foetal hydrops, which can lead to stillbirth.

What mums on our forums are saying… 

“I am a teacher and when I was 20 wks pregnant, there were a few cases of slapped cheek in our school. My midwife advised me to stay away from school and I had to have blood tests. Apparently a lot of adults have had slapped cheek at some point in their life, most of the time without knowing it as it can manifest itself as cold/flu-like illness”. – MrsCox

German Measles (rubella)

German measles or rubella is most dangerous for your baby if you catch it in the first four months of pregnancy – but your midwife will be very vigilant about checking your immunity. If you have come into contact with someone with German measles, see your GP straight away. Symptoms include: a red-pink skin rash made up of small spots, swollen glands, fever, aching joints and cold-like symptoms.

Who might need the test? Your antenatal blood tests will check your rubella status.

What does the test involve? A simple blood test to check your immunity. However, if are not immune, you cannot have the vaccine while you are pregnant so you will need to be more vigilant.

What’s the risk to my baby?

Firstly, German measles are relatively rare now because of the MMR vaccine. If you get German measles during the first four months of your pregnancy, your baby is at greater risk. There is a danger of miscarriage or stillbirth, and can leave your baby with sight, hearing, brain and heart defects – called congenital rubella syndrome (CRS).  After 20 weeks, the risk reduces, although some problems with your baby may only be apparent when they are older. If your baby is affected, your midwife and consultant will encourage you to have counselling and to talk through the options available to you.

What mums on our forums are saying… 

“I’m not immune and at my 25-week appointment, they told me that I’ll be given the MMR vaccine again (had it at school) after I’ve given birth, and advised me to stay away from anyone that had come out in a rash.” – rileysmummy

Read more about rubella in pregnancy here

Your pet cat is pretty clever, mixing purrs with cries that imitate those of a human baby to get the food bowl filled.


Toxoplasmosis is an infection caught from a parasite that is found in cat poo and infected meat. So if you have a cat and are changing litter trays or picking up after your kitty when you are pregnant you need to be very careful and wash your hands afterwards (or ideally avoid any contact with their litter whatsoever). Also be sure to wash fruit and veg well as it may have been contaminated by cat poo.

Who might need the test? Your midwife or doctor can advise you if you are worried you are at risk. Bear in mind, the risks are very low – a study in 2010 found that in non-immune pregnant women (who hadn’t been infected before), only 5 in 1,000 may get the toxoplasmosis infection.

What does the test involve? It’s a simple blood test.

What’s the risk to my baby?

Although very rare, getting toxoplasmosis in the early stages of pregnancy can cause miscarriage, stillbirth and health and developmental problems such as water on the brain, jaundice, epilepsy, cerebral palsy, brain damage, sight issues and deafness.

If you contract it during the third trimester (from week 27 until birth), there is a 70% chance of your baby becoming infected, although they are unlikely to develop serious health problems.

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.

What mums on our forums are saying 

“I have 2 house cats and a dog. My midwife told me to clean my hands after every time I touched the cats, but let’s face it, that’s impossible! I carried on as normal except for changing the litter tray.” – Grudie  


Your iron levels will be tested early on in pregnancy, but anaemia can develop anytime, and leave you feeling wobbly, tired and even prone to fainting. It can be treated with supplements and a diet high in iron-rich food like green leafy veg or red meat.

Who might need the test? If you are feeling faint and dizzy often, your midwife might recommend you have a blood test. Or it could be that iron deficiency is noted during routine blood screening at your booking appointment or at your 28-week check-up.

What does the test involve? It’s a simple blood test.

What’s the risk to my baby?

There is only a risk to your baby if you are severely anaemic. Problems could then arise from early labour, your baby being small for his or her dates, or being born with low levels or iron.

What mums on our forums are saying 

“For best results – and to avoid constipation – take the iron with a glass of orange juice. It helps absorption and keeps things moving along!” – mrsp

Hepatitis B

Hepatitis B is a blood borne viral disease which affects the liver. Mums can pass it on to their unborn babies so screening is very important.

Who might need the test? All mums-to-be are offered a test for Hepatitis B during their antenatal screenings. The virus is spread by contact with infected blood and by having unprotected sex with an infected person.

What does the test involve? It’s a blood test.

What’s the risk to my baby? 

If your baby is at risk of Hepatitis B they will be given a vaccination given within 24 hours of birth, with further doses later on. The vaccine is 90-95% effective in preventing long-term Hepatitis B infection.

Healthy pregnancy diet


Your midwife will be keeping a close eye on you for any signs of gestational diabetes – and if you do get it, it is treatable through diet and sometimes medication. If you are concerned about gestational diabetes, read our in-depth guide to diabetes during pregnancy.

Who might need the test? You’ll be tested if you’ve have had diabetes in pregnancy before, a history of it in your family, or if you’ve already had a very big baby (4.5kg or heavier). Or it could just be because your midwife has found sugar in your urine during one of your routine wee checks. Women of certain ethnic origins or with a higher BMI will also be offered testing.

What does the test involve? You will need to fast overnight and then have a couple of blood tests after having a special sugary drink – your midwife will then compare the results to see what your blood sugars are up to!

What’s the risk to my baby?

Untreated diabetes can cause lots of problems for mum and baby, including congenital abnormalities and problems during labour if your baby grows too large.

What mums on our forums are saying…

“Hey I had GD with DD and went full term to give birth to a healthy girl born 5lb 15oz just had to learn to control my diet!” – JoanneG

Sickle cell and thalassaemia

Sickle cell affects the way red blood cells carry oxygen around the body, and is an is an inherited condition. Thalassaemia causes life-threatening anaemia. Blood test can find out if you’re a carrier of either.

Who might need the test? All mums-to-be are offered testing for thalassaemia, but sickle cell screening depends on whether you are in a higher risk group.

What does the test involve? It’s a blood test which checks for both conditions. It’s best to have it before you are 10 weeks along.

What’s the risk to my baby?

If you are found to be carrying sickle cell or thalassaemia, your baby’s dad will need to be tested too, as your baby could be at risk if you are both carriers. If that is the case, you’ll be offered a diagnostic test on your baby.

What mums on our forums are saying 

“I found I have the sickle cell trait due to being mixed race. Didn’t know I had it, but have read up on it and I’m glad I know as it can be dangerous under certain circumstances. But as a result, the OH had to have his blood taken to be tested for it. The odds of him having it were 1 in 1000 as he is white but even so had to test anyway.” – MrsJC2be

From coughs and colds, to pregnancy headaches and anaemia, it’s always best to talk to your GP or midwife about what’s safe for you to take when you’re pregnant.

Urine infections (UTIs)

Urine infections are pretty common among pregnant women, but as you will give a urine sample at every midwife appointment, these are usually diagnosed quickly.

Who might need the test?

Your midwife should pick up any issues at your antenatal check, but if you have symptoms such frequent peeing, pain when passing water, or cloudy, bloody or discoloured urine, see your GP straight away.

What does the test involve? You will need to provide a urine sample, and your midwife or GP will do a simple test for bacteria. They may prescribe you pregnancy-safe antibiotics to clear up the infection.

What’s the risk to my baby?

Left untreated, a urine infection or cystitis could turn into a kidney infection. In more severe cases, there is a risk of premature labour and consequentially, your baby being born with low birth weight.

What mums on our forums are saying 

“Last time I had a urinary infection I didn’t even realise! I figured it would be like cystitis with all the stinging and peeing frequently. The only symptoms I had was that I started being sick at 4am and by 10 couldn’t even manage small amounts of fluid and really bad lower backache.”-Jen_and_ERB

Read more about UTIs in pregnancy here.


Thrush is really common in pregnancy, so always flag it up with your midwife who can suggest suitable meds for it, as not all over-the-counter products can be used when you’re expecting. Symptoms can include: stinging sensation when you pee, vaginal discharge, itching and soreness around the entrance of the vagina, pain during sex.

Who might need the test? If you describe your symptoms to your midwife, she will probably be able to ascertain straight away if it is thrush, so testing won’t be necessary.

What does the test involve? If it’s not clear from your symptoms or you have a severe or prolonged case of thrush, your midwife or GP will take a vaginal swab to confirm the diagnosis and rule out other infections.

What’s the risk to my baby?

There is very little risk to your baby from thrush – even if they catch it during delivery, it is very easily treated.

What mums on our forums are saying 

“I have got thrush, it feels uncomfortable more than itchy – like a niggle I can feel down below! It’s definitely not as bad as I’ve had it before!” – cupcakeladyj


Chlamydia is a sexually transmitted infection that can be easily treated with antibiotics, even during pregnancy. The problem is that it’s hard to spot. The NHS estimates that 70% of women with chlamydia don’t notice any symptoms. The most common symptoms of chlamydia include: pain when urinating, unusual vaginal discharge, pain or bleeding during or after sex, and tummy or pelvic pain.

Who might need the test? Anyone who thinks they are at risk of having contracted it from their partner.

What does the test involve? It’s a simple urine or vaginal swab test.

What’s the risk to my baby?

Untreated chlamydia puts women at risk of having an ectopic pregnancy, miscarriage or premature delivery. There is also the risk of passing on the infection to your baby during birth so it’s really important to get checked out if you think you’re at risk.

What mums on our forums are saying 

“I had it all through my first pregnancy without knowing, it was only after my daughter was born and I kept bleeding for months that I was sent for a test and it came back positive. I have no idea how long I had it before I conceived but I fell pregnant within a month and our daughter is absolutely fine!” – Faith  


You’ll be offered a confidential HIV test as part of your routine antenatal care.  If your test comes back positive, counselling will be available to you. Current NHS advice states that pregnancy is unlikely to adversely affect an HIV-positive mum who is in good health and without symptoms of the infection.

Who might need the test? Everyone is offered the test – it is entirely up to you if you have it, and your doctor or midwife will discuss what having the test entails.

What does the test involve? It’s a blood test.

What’s the risk to my baby?

HIV-positive mothers can pass the virus on to their baby through breast milk, but mums will be closely monitiered and loooked after during pregnancy and birth.

What mums on our forums are saying 

“My midwife is really nice but she likes mums to do things her way – she was very funny when I turned down the Downs tests and the HIV test.”- spongebobmummypants


Syphilis is bacterial infection which is usually caught from sexual contact. It can also be contracted by sharing drug paraphernalia. In pregnancy, it can be passed from a mum to unborn baby.

Who might need the test? All women are offered screening for syphilis during their early antenatal blood tests.

What does the test involve? It’s a blood test.

What’s the risk to my baby?

If you do not have treatment, syphilis can cause miscarriage or stillbirth and serious health problems for mum, including stroke, blindness or even death.

What mums on our forums are saying 

“I’ve read that STI’s can cause problems in pregnancy if left untreated but I know people who had them and when they got pregnant found out straight away [from screening tests].” – Hal

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