Tommy's PregnancyHub

Group B strep – what you need to know

Group B Streptococcus (GBS) is a type of bacteria carried in the body. Carrying group B strep is usually harmless, but sometimes it can infect a baby during labour. Fortunately, most group B strep infections in newborn babies can be prevented, simply and safely, when pregnant women carrying group B strep are offered antibiotics in labour.

It’s important to know the facts about group B strep – including what the risk factors are and what the key signs of infection are. You can then make an informed decision about what is right for you and your baby. For July’s Strep B Awareness Month, we’ve partnered with the charity Group B Strep Support to highlight the 5 key things you need to know:

1. Carrying or being ‘colonised with’ group B strep is normal

Group B strep is carried by around a quarter of healthy adult women, usually in the vagina and rectum. It doesn’t usually cause any harm or symptoms to women that carry it.

2. On average in the UK, 2 babies a day develop group B strep infection

Group B strep is the most common cause of severe infection in newborn babies. It most commonly causes sepsis (infection of the blood), pneumonia (infection in the lungs) or meningitis (infection of the fluid and lining around the brain and spinal cord) in babies under 3 months.

Most babies will recover fully with quick treatment, but prevention is better than cure.

3. Most group B strep infections in newborn babies can be prevented

Giving intravenous antibiotics (into a vein) during labour to pregnant women who are carrying group B strep reduces the risk of their baby developing a GBS infection in their first week from around 1 in 400 (0.25%) to 1 in 4000 (0.025%).

4. In the UK, women are offered antibiotics in labour in certain circumstances:

These include if:

  • you have a positive GBS test result during your pregnancy (from a private or NHS test)
  • a previous baby had a GBS infection
  • GBS has been found in your urine during your pregnancy
  • your waters break after 37 weeks and you are known to carry GBS
  • you develop any signs of infection in labour
  • you go into preterm labour (before 37 completed weeks of pregnancy)
  • you carried GBS in a previous pregnancy.*

* If group B strep was detected in a previous pregnancy and your baby did not develop an infection, there is a 1 in 2 (50%) chance that you will be carrying it again in your next pregnancy. To help you choose whether you would like to have antibiotics in labour, 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.

5. Testing is the only way to detect group B strep

There are no symptoms to show whether someone is carrying GBS. Tests are not widely available on the NHS, though are available privately. You can visit to find organisations that follow Public Health England guidance.

Most group B strep infections in newborn babies can be prevented by giving antibiotics in labour to women who test positive for GBS or where there are other risks.

Although most common in the first 2 days after birth, GBS infections can develop in babies up to around 3 months old. If your baby shows signs of group B strep infection, call your doctor immediately. If your doctor isn’t available, go straight to your nearest A&E. If a baby has group B strep infection, early diagnosis and treatment are vital – delay  could be fatal.

“Mothers may not know about group B strep (GBS) because these infections are not common in babies and can usually be prevented - but for those few unfortunate families, they can be devastating, so raising awareness is really important. Although other countries offer routine tests for GBS during pregnancy, the UK currently doesn’t, for various reasons: screening is never 100% accurate, and most women carry the bacteria without experiencing any problems, so tests would often lead to unnecessary treatment, putting undue strain on these mothers and the NHS. However, a major research trial has just been funded to establish the best approach for the UK, so this guidance may change in future when the National Screening Committee reviews that evidence.”

Jane Brewin, CEO at Tommy's

About Group B Strep Support

This charity works to give all women in the UK access to up-to-date and accurate information about group B strep. If you’d like more information visit Group B Strep Support.