Tommy's PregnancyHub

Group B strep (strep B) and pregnancy

Group B strep (also known as GBS or strep B) is a common bacteria carried in the body. Carrying group B strep is usually harmless, but sometimes it can infect a baby during labour. GBS infection can make your baby very unwell, but with early treatment most babies will make a full recovery.

What is group B strep?

Group B strep (GBS) is a type of bacteria called streptococcal bacteria. It is very common and lives in the body, usually in the rectum (bum) or vagina. Roughly 20% to 40% of women in the UK carry it.

Carrying this bacteria is usually harmless – most people don’t even realise they have it. But sometimes it can affect a baby around the time of birth and make them poorly. In very rare cases, it can affect a baby during pregnancy. Most babies who develop GBS infection become ill in the first week after birth, but GBS infections can develop in babies up to around 3 months old.

GBS is not a sexually transmitted disease and most women carrying it will have no symptoms.

What could GBS mean for my baby?

Many babies come into contact with GBS during labour or around birth and most of them will stay healthy.

However, some of these babies become seriously ill. Around 1 in every 1,750 newborn babies in the UK and Ireland become unwell in the first week after birth, usually within 12-24 hours of birth. This is known as early-onset GBS infection.

GBS can cause infections such as sepsis, pneumonia and meningitis. A small number (1 in 14) of babies who recover from GBS infection will have a long-term disability. Sadly, a small number (1 in 19) of babies who develop an early-onset GBS infection die.

However, although GBS infection can make your baby very unwell, most babies will make a full recovery with early treatment. 

"I wasn't tested for GBS but it was discovered following a urine sample when I was around 16 weeks pregnant. It was really stressful being diagnosed with group B strep - my pregnancy was tense anyway because I'd already had a son who was stillborn. I was given antibiotics during labour and thankfully our daughter was born safe and well and is now a very boisterous 6 year-old."


Will I be tested for group B strep in pregnancy?

Testing for group B strep is not routinely offered to all pregnant women in the UK. Testing is usually only offered to women who had GBS in a previous pregnancy. It is sometimes found by chance when you have vaginal or rectal swabs or a urine test for other reasons.

Routine testing is a controversial issue in the UK, though it is widely available in most other high-income countries. The UK National Screening Committee does not recommend testing all pregnant women. This is because:

  • Many women carry the bacteria and, in the majority of cases, their babies are born safely and without developing an infection.
  • Screening women late in pregnancy cannot accurately predict which babies will develop GBS infection.
  • No screening test is entirely accurate. For example, between 17% and 25% of women who have a positive swab at 35–37 weeks of gestation will be GBS negative at delivery. And between 5% and 7% of women who are GBS negative at 35–37 weeks of gestation will be GBS positive at delivery.
  • Many of the babies who are severely affected from GBS infection are born prematurely, before the suggested time for screening.
  • Giving antibiotics to all carriers of GBS would mean that a very large number of women would receive treatment they do not need. This could harmful mum and baby.

However, most high-income countries offer universal testing to pregnant women. A major research trial has recently been funded to establish what is the best approach for the UK.

What to do if you're worried about GBS

Understandably, some women feel anxious about not having a routine test for GBS. It’s best to talk to your midwife or GP if you have any concerns about GBS. Although testing isn’t routinely offered to all pregnant women, you can pay for a test privately.

You can find information about getting tested for GBS on the Group B Strep Support website.

If you’ve had GBS in a previous pregnancy

If you have had GBS in a previous pregnancy and your baby was not affected by GBS, you may be offered a test. This is because there is a 1 in 2 (50%) chance that you will be carrying it again in this pregnancy. You can have a swab test (known as the enriched culture medium or ECM test) to see whether you are carrying GBS when you are 35-37 weeks pregnant.

If the result shows that you are still carrying GBS, the risk of your baby developing an infection is around 1 in 400. You will be offered antibiotics in labour.

If you are not still carrying GBS, then the risk of your baby developing an infection is much lower (1 in 5000). You may still be offered antibiotics, but you may choose not to have them.

Is my baby at risk of GBS infection?

Early-onset GBS infection is more likely if:

  • your baby is born prematurely (before 37 weeks of pregnancy) – the earlier your baby is born, the greater the risk
  • you have had a baby before that had a GBS infection
  • you had a high temperature or other signs of infection during labour
  • your waters broke more than 24 hours before your baby is born
  • you have had any positive urine or swab test for GBS in this pregnancy.

How can we reduce the risk of my baby developing GBS infection?

Depending on your circumstances, you may be offered antibiotics through a drip from the start of labour and at intervals until your baby is born. You won’t be offered antibiotics before labour because this does not reduce the chance of your baby developing GBS infection.

These antibiotics reduce the risk of your baby developing a GBS infection in their first week of life from around 1 in 400 to 1 in 4,000. Your healthcare professional should talk to you about the benefits and risks of taking these antibiotics.

If you’ve had a baby with a GBS infection before

If you have already had a baby who was diagnosed with GBS infection, you should be offered antibiotics through a drip from the start of labour in every pregnancy after that.

If you have a positive GBS test

If testing show that you are carrying GBS, you will be offered antibiotics through a drip from the start of labour and at intervals until your baby is born.

If you have a GBS urine infection

If you have a urine infection caused by GBS, you will be offered antibiotic tablets to treat the infection straight away. You’ll also be offered antibiotics through a drip during labour.

If your waters break after 37 weeks and you are carrying GBS

If this happens, you will be offered an induction straight away. This is to reduce the time that your baby is exposed to GBS before birth. You should also be offered antibiotics through a drip.

If you develop any signs of infection in labour

Even if you are not known to carry GBS, you will be offered antibiotics through a drip that will treat a wide range of infections including GBS.

If you go into premature labour

If your labour starts before 37 completed weeks of pregnancy, your healthcare professional will recommend that you have antibiotics through a drip even if you are not known to carry GBS.

If you are having a planned caesarean section

If you are carrying GBS and have a caesarean section planned (including a preterm section), you do not need antibiotics to prevent GBS infection in your baby. This is unless labour has started or your waters have broken.

All women having a caesarean section will be offered antibiotics at the operation. This is to reduce the risk of a wide variety of infections, including GBS.

“I had tested positive for GBS during previous pregnancies, so I was offered antibiotics during labour with my youngest son. I was being induced due to an unrelated complication and had a history of fast deliveries and so was given my first dose of antibiotics before having my waters manually broken. It ended up being my only dose as our little boy was born 3 hours later. Having the drip didn't affect my labour at all, I was mobile and active during labour. It gave us enormous peace of mind to know that the antibiotics had minimised the chance of him developing a GBS related infection.”


What are my options for where I can have my baby?

Your midwife or doctor will talk to you about your birth plan and where and how you want to give birth. You should always let your healthcare professional know if you have previously had a baby who had GBS infection or if you have tested positive for GBS in this pregnancy.

If you need antibiotics during labour, they will need to be given through a drip. This means that it may not always be possible to arrange this at home or in some midwifery-led units.

Find out more about your options for where to give birth.

Having antibiotics shouldn’t stop you from moving around freely during labour or from having a water birth, if that’s what you want.

If your waters break before labour, your healthcare professional will talk to you about when you will need antibiotics and about the best time for your baby to be born. This will depend on your individual circumstances and on how many weeks pregnant you are.

If you know you need antibiotics in labour, contact your healthcare professional as soon as labour starts or your waters break. It is important that you have antibiotics as soon as possible.

Will my baby be monitored for GBS after they are born?

If your baby is born at full term (after 37 completed weeks) and you had antibiotics in labour at least 4 hours before giving birth, they will not need special monitoring after birth.

If your baby is thought to be at higher risk of GBS infection and you did not get antibiotics at least 4 hours before giving birth, they will be monitored closely for signs of infection for at least 12 hours. This will include assessing your baby’s general wellbeing, heart rate, temperature, breathing and feeding.

If you have had a baby affected by GBS infection before, your baby will be monitored for 12 hours even if you had antibiotics in labour.

The chance of your baby developing GBS infection after 12 hours is very low. You and your baby won’t need antibiotics after this, unless either of you become ill.

What are the signs of GBS infection in my baby?

Babies with early-onset GBS infection may have the following symptoms:

  • grunting, noisy breathing, moaning, seeming to be working hard to breathe when you look at their chest or tummy or not breathing at all
  • be very sleepy and/or unresponsive
  • be crying inconsolably
  • be unusually floppy
  • not feeding well or not keeping milk down
  • have a high or low temperature and/or their skin feels too hot or cold
  • have changes in their skin colour (including blotchy skin)
  • have an abnormally fast or slow heart rate or breathing rate
  • have low blood pressure or low blood sugar (tests for these are done in hospital).

If you notice any of these signs or are worried about your baby, you should contact your healthcare professional urgently and tell them you are concerned it may be GBS. If your baby has GBS infection, early treatment will give them the best chance of recovery.

What tests and treatments will my baby have?

If your healthcare professional thinks that your newborn baby has an infection, they will do tests to see if it is caused by GBS. This may involve doing a blood test, or a sample of fluid will be taken from around your baby’s spinal cord (known as a lumbar puncture).

You will be asked for your consent (permission) before these tests are done.

Babies with signs of GBS infection or babies who are suspected to have the infection should be treated with antibiotics as soon as possible. Treatment will be stopped if there is no sign of infection after at least 36 hours, and all the tests are negative.

Can I still breastfeed if my baby has a GBS infection?

Yes, it is safe to breastfeed your baby. Breastfeeding has not been shown to increase the risk of GBS infection, and it offers many benefits to both you and your baby.

Could my baby develop GBS infection after their first week of life?

Most (two-thirds) GBS infections in babies are in the first week after the birth. A third of GBS infections in babies are late-onset, which means they happen between 7 days to 3 months after birth.

Having antibiotics during labour does not prevent late-onset GBS infection, and there are currently no known ways of preventing late-onset GBS infections.

Call 999 or go to A&E if your baby gets any of these symptoms:

  • being floppy and unresponsive
  • grunting when breathing
  • an unusually high or low temperature
  • very fast or slow breathing
  • a very fast or slow heart rate.

They may need treatment with antibiotics in hospital immediately.

More information and support

Group B Strep Support is a UK charity working to stop group B strep infections in babies. They provide up to date and evidence-based information on group B strep to new and expectant parents and their health professionals, and support to affected families.

Group B Strep Support and the Royal College of Obstetricians & Gynaecologists. (Group B Streptococcus in pregnancy and newborn babies (Published in December 2017 Next Update due 2020)

Review dates
Reviewed: 01 July 2020
Next review: 01 July 2023