Group B strep in pregnancy: testing, risks and decisions
Group B streptococcus (GBS) is a common bacterium that many people carry without knowing it. For most pregnant women, it causes no problems at all. However, in rare cases it can be passed to a baby during birth and lead to serious illness in the newborn. Understanding what GBS is, how the NHS approaches it, and what your options are can help you have an informed conversation with your midwife or doctor as you approach the end of your pregnancy.
What is group B streptococcus?
Group B streptococcus is a type of bacterium that lives naturally in the gut and vagina of around one in four women. Carrying GBS is entirely normal, causes no symptoms and is not a sign of illness or poor hygiene. Most women who carry GBS have straightforward pregnancies and healthy babies. The concern arises because during labour and birth, the bacterium can occasionally pass from the birth canal to the baby. When this happens, it can in rare cases cause serious infections including sepsis (blood poisoning), pneumonia or meningitis in the newborn. The risk to any individual baby is low, but because the consequences of infection can be severe, it is taken seriously by healthcare professionals.
How is GBS managed in UK pregnancies?
Unlike in the United States and several other countries, the NHS does not offer routine GBS screening to all pregnant women. The UK currently takes a risk-factor based approach: rather than testing everyone, midwives and doctors look for specific circumstances that suggest a higher chance of GBS causing a problem for the baby. If you meet one or more of these criteria, you will be offered antibiotics during labour to reduce the risk of passing GBS to your newborn.
The situations in which intravenous antibiotics are offered during labour include:
- GBS has been found in a swab or urine sample at any point in your current pregnancy
- A previous baby of yours had a GBS infection
- You develop a fever during labour
- Your baby is being born prematurely
If GBS is detected in your urine during pregnancy (rather than on a swab), you will also be treated with antibiotics straight away, as well as being offered them again in labour. Intravenous penicillin is the most commonly used antibiotic. It significantly lowers the risk of GBS being transmitted to the baby, though it does not eliminate that risk entirely.
How GBS is sometimes discovered
Because there is no routine screening programme, GBS is often found incidentally. A urine sample taken for another reason, such as investigating a suspected urinary tract infection, may come back positive for GBS. Similarly, a vaginal swab carried out for another purpose may detect the bacterium. If this happens, your midwife or doctor will talk you through what it means and what happens next. Finding GBS in this way does not mean you are unwell; it simply confirms that you are a carrier and allows your care team to plan accordingly for labour.
Private GBS testing
Some pregnant women choose to find out whether they are carrying GBS by arranging a private test, particularly if they want certainty going into labour but do not meet the NHS criteria for antibiotic prophylaxis under the risk-factor approach. The most sensitive method available is an enriched culture medium (ECM) test, which involves taking vaginal and rectal swabs at between 35 and 37 weeks of pregnancy. This is the testing method most likely to give an accurate result, but it is not routinely available through the NHS.
If you would like to explore private testing, the charity Group B Strep Support (gbss.org.uk) is a reliable starting point. It provides information about how to access an ECM test, what the result means, and how to discuss it with your maternity team. Private laboratories also offer this test directly. Whatever the result, it is worth discussing it with your midwife so that any appropriate plans for labour can be put in place.
Recognising GBS infection in a newborn
If you carry GBS and antibiotics in labour were not given, or if you are simply aware of the possibility of GBS, it is useful to know what signs of infection to look out for in your baby after birth. GBS infection in newborns can develop quickly, sometimes within the first few hours, or it may take a day or two to become apparent. Early signs that something may be wrong include a temperature that is unusually high or unusually low, poor or refused feeding, grunting or laboured breathing, floppiness, changes in skin colour, and a high-pitched or otherwise unusual cry.
These symptoms warrant urgent medical attention. If you are at all concerned about your newborn in the days after birth, contact your midwife, call NHS 111, or go to your nearest emergency department without delay. GBS infection in a newborn is treatable, but prompt treatment makes an important difference to outcomes.
Frequently asked questions
Is GBS testing routine in the UK?
No. The NHS does not currently offer routine screening for group B strep to all pregnant women. Research has not yet demonstrated that universal screening improves outcomes compared to the current risk-factor based approach. The charity Group B Strep Support advocates for routine screening and can provide more information on the debate.
Can I test for GBS privately?
Yes. A private enriched culture medium (ECM) test, a vaginal and rectal swab done at 35 to 37 weeks, is the most accurate way to detect GBS. It is not routinely available on the NHS but can be arranged through private laboratories. The charity Group B Strep Support (gbss.org.uk) has information on obtaining a test.
What happens if GBS is found during my pregnancy?
If GBS is detected in your urine during pregnancy, you will be treated with antibiotics immediately. If it is found on a swab, you will be offered antibiotics through a drip during labour. Antibiotics in labour significantly reduce the chance of GBS being passed to the baby.
What are the signs of GBS infection in a newborn?
Signs can develop within hours or days of birth. They include a high or unusually low temperature, poor feeding or refusing to feed, grunting or unusual breathing, floppiness, abnormal skin colour and a high-pitched or unusual cry. GBS infection in a newborn is a medical emergency: seek care immediately if you are concerned.
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