By Lindsay Norris
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  1. What is Group B Strep (GBS)? Group B Streptococcus (GBS) is a very common bacterium. It occurs naturally in many people, from babies to the elderly, and typically causes no harm or symptoms. Carrying GBS (also called GBS colonisation or GBS carriage) is entirely normal - up to one in every three people carries GBS in the gut (bowel), and in women it is often also found in the vagina.

    Carrying GBS can be intermittent - it can come and go - but simply carrying GBS does not require treatment.

    The time it is important to know whether you carry GBS is during pregnancy. GBS can cause devastating infections, most commonly in newborn babies before, during or shortly after birth. Thankfully, these infections are relatively rare - approximately one in every 1,000 babies. GBS occurs in babies where no preventative action is taken. But this still means that UK wide, 700 babies a year develop GBS infection - usually septicaemia, pneumonia and/or meningitis. Most fully recover, but around 10% of babies infected with GBS die and survivors can be left with serious mental or physical disabilities.

    Unless you have a test designed to find it, you are unlikely know whether you carry it or not as there are no symptoms of GBS colonisation.

  2. How do I find out if I am carrying GBS? You can find out if you carry GBS by having a test, involving swabs taken from the vagina and rectum. These tests are not routine but, when they are taken, they are most commonly carried out between 35 and 37 weeks of pregnancy.

    The "Gold Standard" test for detecting GBS carriage is called the ECM (Enriched Culture Medium) test and is available privately (see below) and from a handful of NHS hospitals. This test uses both vaginal and rectal swabs to detect the bacteria and is highly predictive of whether you are carrying GBS for approximately 5-6 weeks.

    A vaginal swab taken within the NHS will sometimes find the bacteria. A positive result is highly reliable and means you are carrying GBS. Unfortunately a negative NHS test result is not as reliable - up to 50% of women carrying GBS when the swab is taken will be given a false negative result.

    GBS carriage can come and go but an ECM test done at 35 - 37 weeks of pregnancy is highly predictive of carriage status at birth.

    Two private laboratories that can offer ECM testing by post are:

  3. If I have a positive result from a GBS swab what should I do? Simply carrying GBS does not require treatment. If you are found to carry GBS, you should be offered intravenous antibiotics in labour to minimise the risk of GBS infection developing in your baby. Over 80% of GBS infection in newborn babies can be prevented when women are routinely screened for GBS carriage late in their pregnancy and when those found to carry GBS, plus those with other recognised risk factors, are offered intravenous antibiotics as soon as possible once labour has started. The other recognised risk factors are:
    • The mother has previously had a baby infected with GBS - risk is increased 10 fold
    • The mother has been found to carry GBS in this pregnancy or GBS has been found in the urine at any time during this pregnancy - risk is increased 4 fold

    Any of the following clinical risk factors - risk of GBS infection is increased 3 fold

    • Labour starts or membranes rupture before 37 weeks of pregnancy is completed
    • Where the waters (membranes) have broken more than 18 hours before the baby is born
    • Where the mother has a temperature during labour of 37.8°C or higher.

    If GBS is found in your urine at any time during your pregnancy, then this is an infection and should be treated promptly with oral antibiotics. It is also an indication that you should be offered intravenous antibiotics when you go into labour.

    Giving antibiotics to women who are simply carrying GBS is not effective at preventing GBS infection in babies.

For more information about GBS, speak with your doctor or midwife, or call the national charity Group B Strep Support on 01444 416176, or look at their website www.gbss.org.uk

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