Read time 7 minutes

Show References
Pregnancy conditions

It can be a complication of pregnancy but many people don’t know about it. Here’s the lowdown.

What is Group B Streptococcus (GBS)?

Group B Streptococcus is also known as GBS, Strep B or Group B Strep. It is a common bacterium that normally causes no harm (NHS, 2021). Even when you’re pregnant or have just had a baby, having GBS isn't usually a problem. However, rarely it can cause a serious infection (RCOG, 2017).

In the UK, 2 to 4 in 10 women carry GBS in their vagina and rectum. It is not a sexually transmitted disease, but a normal bug. You’re unlikely to know you carry it as there are no symptoms (RCOG, 2017).

Group B Streptococcus and pregnancy

If you have Group B Streptococcus, your baby will probably be exposed to it around labour and birth. While most babies won’t be affected, there is a very small chance of your baby becoming seriously ill. In extremely rare cases GBS infection can cause miscarriage, early labour or stillbirth (NHS, 2021).

The risk of your baby getting GBS infection is higher if:

  • your baby was born before 37 weeks (the risk is higher the more premature they were)
  • you previously had a baby who developed GBS infection
  • you had a high temperature during labour
  • you had any positive urine or swab tests for GBS in this pregnancy
  • your waters broke more than 24 hours before your baby was born. (RCOG, 2017)

Early-onset Group B Streptococcus

Around 1 in every 1750 babies in the UK and Ireland is diagnosed with early-onset GBS (RCOG, 2017). This is picked up in the first week after birth and treated promptly. Most of these infected babies develop symptoms within 12-24 hours of birth (RCOG, 2017).

Signs of GBS to watch out for are:

  • breathing is effortful, noisy, very fast or slow, or not visible
  • being floppy and/or unresponsive
  • not feeding well or vomiting milk up
  • very high or low temperature/skin feels too hot or cold
  • very fast or slow heart rate
  • irritability
  • crying inconsolably
  • changes in their skin colour, including blotchy skin (RCOG, 2017).

Contact your healthcare professional urgently, or go to the Emergency department, if you notice any of these signs or are worried about your baby. Mention GBS. Early treatment can be lifesaving (RCOG, 2017).

Late-onset Group B Streptococcus

Late-onset GBS is less common, and develops between seven days and three months after a baby is born. This condition is not associated with pregnancy so your baby has picked up the infection after birth.

If you're concerned about your baby, talk with a health professional urgently.

Complications of GBS

Most babies with GBS infection will make a full recovery. However, sometimes the infection can lead to complications like:

  • sepsis
  • pneumonia
  • meningitis (RCOG, 2017).

Of the babies who develop an early-onset GBS infection, almost 9 in 10 (87.4%) make a full recovery. One in 19 (5.2%) die and another one in 14 (7.4%) babies have a long-term disability. The complications of early-onset GBS for the baby include hearing loss or loss of vision (NHS, 2021).

Rarely, GBS can cause infection in the mother’s womb or urinary tract, or sepsis (NHS, 2018).

Group B Streptococcus testing in the UK

The NHS does not routinely test for GBS in pregnant women (RCOG, 2017). This is because: it’s uncommon for GBS to give your baby an infection; tests are not accurate enough; and many babies affected by it are born earlier than when they’d be screened (RCOG, 2017). It would also mean that many women would have treatment in labour that they do not need, and which could affect the progress of their labour (RCOG, 2017).

However, if you had GBS in a previous pregnancy, but your baby was not affected, you can discuss having an additional test at 35-37 weeks to check if you are carrying GBS this time (RCOG, 2017).

Some women choose to get tested privately (NHS, 2021).

Reducing the risk in newborn babies

You will be offered antibiotics through a drip during labour if:

  • you have tested positive for GBS
  • GBS has caused a urine infection
  • you previously had a baby diagnosed with GBS infection
  • your waters break after 37 weeks (before your contractions start) and you know you carry GBS (in such cases, you’ll be offered induction to reduce the time your baby is exposed to GBS. You can accept or decline induction)
  • you develop any infection during labour, even if it is not confirmed that you carry GBS
  • your labour starts before 37 weeks.

You can accept or decline antibiotics.

Deciding about antibiotics in labour

Antibiotics reduce the chance of your baby picking up GBS from 1 in 400 to 1 in 4000 (RCOG, 2017). The decision to accept or decline antibiotics is yours, and you are encouraged to be curious about your care so you can make a decision that is right for you (RCOG, 2017). 

  • Antibiotics are given through a drip at intervals, usually four hourly, during labour 
  • You should be enabled to move freely, and labour in water if you wish 
  • Tell your healthcare provider if you are allergic to penicillin or any other medications so an alternative can be offered 
  • Some women experience some sickness or diarrhoea (RCOG, 2017) 

Accepting antibiotics may limit birthplace options (RCOG, 2017). You could discuss possibilities for home or midwife-led-unit birth with a senior midwife if necessary. 

You can also discuss what to do when you go into labour or if your waters break before contractions start.

Antibiotics are not needed if the baby will be born by planned caesarean. However, if labour has started or the waters have broken, they will be offered. Women having a caesarean are offered antibiotics for a wide range of infections (RCOG, 2017).

Tests and treatment for babies

If you decide not to have antibiotics in labour then your baby will be monitored more closely for 12 hours after birth (RCOG, 2017).

If you had antibiotics during labour then your baby will not have additional monitoring, unless you have previously had a baby affected by GBS (RCOG, 2017)

If an infection is suspected in your baby, a doctor will discuss with you if further tests are needed. This could include taking a sample of their blood or the fluid from around their spinal cord (RCOG, 2017). Babies with suspected or confirmed GBS will be offered antibiotics immediately (RCOG, 2017). If there is no sign of infection after 36 hours, any treatment will be stopped (RCOG, 2017).


Breastfeeding your newborn baby is protective for both you and your baby, and there is no reason not to breastfeed if your baby has signs of GBS (RCOG, 2017).

This page was last reviewed in Jan 2022

Further information

Our support line offers practical and emotional support with feeding your baby and general enquiries for parents, members and volunteers: 0333 257 5604.

We also offer antenatal courses which are a great way to find out more about birth, labour and life with a new baby.

Make friends with other parents-to-be and new parents in your local area for support and friendship by seeing what NCT activities are happening nearby.

For more information, visit the Group B Strep Support website here.

RCOG. (2017) Group B Streptococcus (GBS) in pregnancy and newborn babies. Available from: [Accessed 6 January 2022].

NHS. (2018) What are the risks of group B streptococcus (GBS) infection during pregnancy. Available from: [Accessed 6 January 2022].

NHS. (2021) Group B Strep. Available from: [Accessed 6 January 2022].

Related articles

Pregnancy conditions

Courses & workshops

In-person NCT Antenatal course

Find out more

NCT Antenatal refresher course

Find out more
NCT Membership
Support NCT Charity by becoming a member
Excited couple holding pregnancy test
Sign up to our weekly Pregnancy & Baby Guide