Infections in pregnancy that can affect your baby, including group B strep

Group B strep is common in pregnancy and rarely causes problems, and testing for it depends on where you live. Some other infections are worth raising with your midwife or doctor early, and simple habits lower the chance of catching them.

What group B strep is

Group B strep (GBS, sometimes called strep B) is a type of bacteria that usually lives in the bottom (rectum) or vagina. The NHS says it’s very common and most people with it won’t realise. ACOG says about 1 in 4 pregnant women carry it. It isn’t a sexually transmitted infection.

The concern is for the baby. GBS causes no problems in most pregnancies, but now and then it passes to the baby during labour and makes them ill. The NHS puts this at about 1 in 1,750 pregnancies. In newborns, GBS can cause sepsis, pneumonia or meningitis. Most babies who are treated make a full recovery, though some are left with lasting problems such as hearing loss.

Testing depends on where you live

Advice on testing differs between countries.

Where	What the guidance says
UK	No routine testing. The UK National Screening Committee doesn’t recommend screening, and the NHS says tests are rarely done on the NHS. You can pay for a test privately.
US	Routine screening. ACOG says the test is now done between 36 and 38 weeks of pregnancy, using a swab from the vagina and rectum.
WHO	WHO’s 2024 guideline says pregnant women should be offered screening around 35–37 weeks, with a risk-based approach where universal screening isn’t feasible.

The UK committee gives several reasons. A test a few weeks before labour can be positive when the result at birth would be negative. There’s no way of telling which babies will be affected. And screening could mean giving many women antibiotics they don’t need. Its recommendation rests on a review completed in March 2017, and it plans to look at the evidence again once the GBS3 trial ends. That trial compares screening in late pregnancy or labour with the current UK approach, which is based on risk factors, so UK advice may change when it reports.

GBS is sometimes found anyway, during a urine test or vaginal swab done for another reason. If you’re in the UK and worried, talk to your midwife or GP about the risks to your baby and whether to get tested.

Antibiotics during labour

When GBS is found, the usual step is antibiotics through a drip into a vein once labour has started. ACOG says labour is the best time for this treatment. It helps prevent infection in the baby’s first week, but it doesn’t prevent illness that starts later.

The NHS says you should be offered antibiotics in labour if a previous baby had a GBS infection, or if you’ve had a GBS urine infection in this pregnancy. Your midwife or doctor will also look at other things that make infection in the baby more likely:

• going into labour before 37 weeks
• labour not starting within 24 hours of your waters breaking
• a high temperature during labour
• currently carrying GBS

ACOG lists similar reasons to give antibiotics without a test, including when your GBS status isn’t known and it has been 18 hours or more since your waters broke. If you’re allergic to penicillin, tell your health care professional before you’re tested. Other antibiotics can be used if needed.

If your waters break before labour starts, the NHS suggests taking your temperature every 4 hours while you’re awake and telling your midwife if it’s raised. Tell them immediately if the fluid changes colour or smell.

If you carry GBS, you may be advised to give birth in hospital and to contact your midwife as soon as labour starts or your waters break. You may also be asked to stay in for at least 12 hours afterwards so your baby can be monitored, though this isn’t always necessary.

Signs of infection in a newborn

ACOG says a baby with early-onset disease typically gets sick within 12 to 48 hours after birth or up to the first 7 days. Occasionally, symptoms develop up to 3 months after birth, so these signs are worth knowing once you’re home, even if nobody told you that you carry GBS. The NHS lists:

• being floppy or not responding as usual
• grunting when breathing, or working hard to breathe
• very fast or slow breathing
• an unusually high or low temperature
• changes in skin colour, or blotchy skin
• not feeding well, or vomiting milk up
• an unusually fast or slow heart rate

ACOG adds lack of energy, irritability, poor feeding and high fever. For any of these, the NHS says to call 999 or go to A&E, and ACOG says to contact your baby’s health care professional right away.

Chickenpox, slapped cheek and rubella

With these, speed matters. Chickenpox in pregnancy can be dangerous for you and your baby. Most adults in the UK are already immune, but if you’ve never had it, or aren’t sure, and you’ve been near someone who has it, the NHS says to speak to your GP, obstetrician or midwife immediately. A blood test can show if you’re immune.

Slapped cheek syndrome is common in children and usually causes a rash on the face. It’s highly infectious and can be harmful to the baby, although in most cases the baby isn’t affected. If you’ve been in contact with someone who has it, talk to your doctor, who can check with a blood test if you’re immune.

Rubella is uncommon in the UK thanks to the MMR vaccine, but catching it in the first 4 months of pregnancy can lead to serious problems. Contact your GP or midwife as soon as possible if you’ve been near someone with rubella, or if you have a rash or have been near anyone who does. The MMR vaccine can’t be given in pregnancy. If you haven’t had both MMR jabs, the NHS suggests asking for it at your 6-week postnatal check.

CMV and young children

Cytomegalovirus (CMV) is a common virus that young children catch often. Most people who have it notice no symptoms. In pregnancy it can cause problems for the baby, including hearing loss, and CDC says about 1 in 200 babies is born with congenital CMV infection. The NHS says CMV is particularly dangerous to the baby if you haven’t had it before.

You can’t always avoid it, but you can lower the chance by limiting contact with young children’s saliva and pee:

• wash your hands with soap and water, especially after changing nappies (diapers)
• don’t share food, cutlery or drinking glasses with young children, or put their dummy (pacifier) in your mouth
• kiss young children on the head rather than the face, or give them a hug

This matters most if your job brings you into close contact with young children.

Toxoplasmosis and animals

Cat faeces and sheep can both carry the organism behind toxoplasmosis, which can harm your baby. The NHS advises avoiding emptying cat litter trays while you’re pregnant. If nobody else can, wear disposable gloves and clean the tray daily. Wear gloves for gardening and wash your hands afterwards. Avoid lambing, milking ewes and contact with newborn lambs, and tell your doctor if you get flu-like symptoms after contact with sheep.

Genital herpes and other STIs

Genital herpes can be dangerous for a newborn baby. Treatment is available if your first infection happens in pregnancy. If it happens near the end of pregnancy or during labour, a caesarean may be recommended to lower the chance of passing herpes on. Tell your midwife or doctor if you or a partner have recurring herpes or develop sores.

Many STIs have no symptoms but can affect a baby’s health. If you think you or a partner may have one, get a check-up as soon as possible.

When to call someone

Call 999 or go to A&E in the UK, call 911 in the US, or your local emergency number, if your baby shows any of the signs above. Do the same for yourself if you’re breathing very fast, are confused, have blue, pale or blotchy skin, or have a very high or very low temperature or are shivery. These can be signs of sepsis, a serious reaction to an infection that needs urgent treatment in hospital.

Whatever your GBS status, call your midwife or maternity unit straight away if your waters break, or if you’re less than 37 weeks pregnant and think you might be in labour. Don’t wait until the next day, even in the middle of the night, and if you can’t reach them in the UK, call 111. If you carry GBS, call as soon as labour starts or your waters break.

Get advice the same day after chickenpox contact if you aren’t immune, or for a rash or rubella contact. Slapped cheek contact and questions about testing can go to your midwife or doctor.