Expert / 7 August, 2020 / My Baba

Everything You Need To Know About Group B Strep & Pregnancy

Do you know about group B Strep?

Expecting a baby can be one of the best times of your life. So it is good to know about group B Strep during pregnancy because, although it can cause severe infections in newborn babies, most of these infections are preventable.

What is group B Strep infection?

Group B Strep is the most common cause of life-threatening infection in newborn babies in the UK and of meningitis in babies up to the age of three months. It is more common than spina bifida and as common as Down’s syndrome, yet many pregnant women have not heard of it.

Although rarely dangerous to adults, a pregnant woman who is carrying group B Strep can pass it on to her baby, particularly around birth. At least 800 babies a year in the UK develop group B Strep infection. One in 20 of these sick babies die, one in 10 survivors suffers long-term problems, and five in 10 survivors of group B Strep meningitis suffer long-term mental and physical problems. Approximately 6 in every 10 of these infections in babies develop in the first week of life (and usually on day one) and these are described as early-onset group B Strep infections. The remainder – the late-onset group B Strep infections – develop from day 7 up until age 3 months, after which time they are very rare indeed.

The good news is that with prompt and appropriate treatment, most babies will fully recover from their group B Strep infection – but prevention is better than cure.

How do I know if I am carrying group B Strep?

Most people don’t know if they carry group B Strep as there are no symptoms. Those who do know they carry it often find out from tests taken during pregnancy, usually for other reasons.

How can I prevent my baby developing group B Strep infection?

Most early-onset group B Strep infections can be prevented.

Testing all pregnant women for group B Strep as a routine part of a pregnant woman’s antenatal care is not currently recommended in the UK, although this is routine practice in most developed countries.

Instead of testing all pregnant women, current national guidance on prevention uses a maternal ‘risk-factor’ approach to predict which newborn babies are likely to develop group B Strep.

These risk factors include:

  • Mum has had a previous baby who had group B Strep infection
  • Group B Strep is found in Mum’s urine or on a vaginal or rectal swab this or a previous pregnancy (though women where group B Strep was detected in a previous pregnancy should be offered the option to having a specific test for group B Strep carriage in this pregnancy)
  • Mum has a high temperature in labour (38 c or higher)
  • Labour starts or waters break before 37 weeks of pregnancy.

In any of these situations, the Mum should be offered intravenous (IV) antibiotics given at intervals from the start of labour or from when the risk factor becomes apparent and then at regular intervals until the baby is born. When given appropriately in labour to a woman carrying group B Strep, these antibiotics have been shown to reduce the risk of the baby developing early-onset group B Strep infection by over 90%.

Sadly, the risk-based approach seems to have had little impact on the rate of early-onset group B Strep infections in babies – the rate has risen since guidelines were introduced in 2003.  Approximately half to two-thirds of the babies who develop early-onset group B Strep infection are born to mothers without any of these risk factors, other than the mother unknowingly carrying group B Strep. Risk-factors are not accurate predictors of which babies will develop group B Strep infection.

Testing is the only way to identify whether a woman is carrying group B Strep. If group B Strep is found during the current pregnancy, then steps can be taken to minimise the risk of the infection in newborn babies – offering Mum, where group B Strep carriage has been detected in the current pregnancy, intravenous antibiotics at the start of labour and at intervals until delivery.

“I want a test – where do I go, what do I ask for and when should I have it”?

The UK National Screening Committee (UK NSC) does not recommend routine antenatal testing for all pregnant women, although the Royal College of Obstetricians & Gynaecologists (RCOG) recommends that the offer of a test should be discussed in certain circumstances.

If group B Strep was found in a previous pregnancy and your baby was unaffected, then you can have a specific swab test (known as the ECM test) to see whether you are carrying group B Strep when you are 35-37 weeks pregnant.

You can ask your midwife about testing, including whether the ECM test is available at your trust, or you can order a home-testing pack privately (approximately £40).

Not all tests for group B Strep are the same

In the past, a general-purpose test, used when a woman has vaginal symptoms, used to be the only test available to detect group B Strep carriage. This involved taking a high vaginal swab (HVS) sample, which was then processed in the laboratory using standard culture plates. Unfortunately, the HVS test is not good at detecting group B Strep – it only finds it in about half the times it is present, so around half (50%) of those carrying group B Strep will be incorrectly told they are not. A positive test result is very reliable, however.

This enriched-culture medium (ECM) test is specifically designed to detect group B Strep and is recommended by the RCOG and Public Health England (PHE) for detecting group B Strep carriage.

The ECM test is not yet available from all NHS trusts although, following the latest RCOG guidance, that is changing. If your trust does not offer the ECM test, or you are not eligible for it within the NHS, you can order your home-testing packs from a number of private companies. Visit GBSS.


Testing for group B Strep at 35-37 weeks of pregnancy is good at predicting the likelihood of your carrying group B Strep when you are most likely to go into labour – in the next five weeks. When performed within five weeks of birth, a negative ECM test result is 96% predictive of NOT carrying group B Strep at birth and a positive ECM test result is 87% predictive of still carrying group B Strep at birth. Earlier testing means your status may be more likely to change. Later testing means there’s a greater chance that your baby will arrive before the test result.

The test came back positive, what happens now?

Knowing you are carrying group B Strep is good news because with that knowledge you can take the appropriate preventative measures. By identifying mums whose babies are at higher risk of group B Strep infection, and offering the most appropriate care during pregnancy and birth, most early-onset group B Strep infections can be prevented.

Any positive group B Strep result means that the pregnant woman should be offered IV antibiotics from the start of labour or waters breaking and then usually at four-hourly intervals until birth.

Mums who have had a previous baby who developed group B Strep infection should always be offered IV antibiotics from the start of labour in subsequent pregnancies (no testing needed).

If you’d like a ‘GBS Alert’ sticker to put on your hand-held pregnancy notes to remind your doctor or midwife about the IV antibiotics in labour, you can download one from GBSS’s website.

A helpful way to keep all this information in perspective is to remember MUMMY:

M – many women carry group B Strep naturally
U – usually causes no problems, but can be devastating
M – most common cause of serious infection in newborns and of meningitis in babies under 3 months
M – most group B Strep infections in babies are preventable
–  your knowledge can help protect your baby

Dr Chris Steele MBE, family doctor and patron of charity Group B Strep Support says, “Group B Strep infections can be devastating but can usually be prevented – get informed and protect your baby.”

Group B Strep Support (GBSS) is a UK charity working to stop group B Strep infection in babies. We educate the public, doctors and midwives about group B Strep and provide information and support to affected families.

Please sign and share the group B Strep petition calling for pregnant women to be informed about group B Strep and offered group B Strep-specific tests in pregnancy.

For free information on group B Strep, please visit GBSS. You can also read more about group B Strep on the NHS website. 

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