Carrying group B Strep (GBS) is perfectly normal and natural. It is normal gut flora in 20-30% of people (men and women), and ‘colonises’ the vagina in roughly 22% of all women. Although GBS can be passed through sexual contact, it is not a sexually transmitted disease, and carrying the bacterium is not associated with any health risks or symptoms to the carrier.
In the UK, pregnant women are not routinely offered testing for group B Strep, unlike in many other developed countries.
Group B Strep will sometimes be detected when samples are taken for other reasons – for example, from a urine sample, or from a vaginal or rectal swab. But often it’s not detected, because the test widely used within the NHS was not developed to find group B Strep and, unsurprisingly, is not very good at doing so. The standard ‘non-specific’ tests used within the NHS give a high proportion of falsely-negative results, though a positive result is reliable.
Sensitive tests designed to detect group B Strep carriage are available, but rarely within the NHS. If you’re interested in finding out whether you carry group B Strep, you can test using the sensitive ‘ECM’ test (visit www.gbss.org.uk/test). The ECM (or Enriched Culture Medium) test is recognised as the ‘gold standard’ for detecting group B Strep carriage (click here to read the guidelines for this test).
It’s good to know whether you carry group B Strep during your pregnancy. If you do, preventative action can be taken to minimise the chance of your newborn baby developing group B Strep infection.
If group B Strep is detected at any time during your pregnancy, you should be offered intravenous antibiotics from the start of your labour and at intervals until your baby is born.
View our medical panel’s recommended approach to preventing GBS infection in newborn babies click here
No treatment for GBS carriage (GBS detected from vaginal or rectal swabs) is required or shown to be beneficial before labour starts, since no antibiotics tested so far have been shown reliably to eradicate GBS carriage.
UK guidelines from NICE and from the Royal College of Obstetricians & Gynaecologists recommend that you should be offered intravenous antibiotics as soon as possible once labour starts and then at regular intervals until the baby is born. This has been shown to be highly effective at preventing GBS infection in newborn babies.
Urinary tract infections caused by GBS during pregnancy should be treated at the time of diagnosis in addition to Mum being offered intravenous antibiotics in labour
For more information about GBS detected in the urine, click here.
Not every pregnant Mum who has GBS detected during her pregnancy will want intravenous antibiotics in labour. Many will, but others may decide not to have them unless there are other additional risk factors. Only a relatively small percentage of babies born to Mums carrying GBS at delivery will develop GBS infection. If you do decide against antibiotics in labour, it would be prudent for your newborn baby to be observed by trained staff for at least 12 hours.
Risk factors for group B Strep infection
Pregnant women carrying group B Strep is perfectly normal. GBS can be present at any time – in a woman’s first pregnancy, or in one or more subsequent pregnancies. It can be a threat during pregnancy, around delivery and afterwards. There are certain situations which increase the chance that a newborn baby may, if susceptible, develop GBS infection. Each of the risk factors shown below increases the risk of GBS infection in a newborn baby:
- Mothers who have previously had a baby infected with GBS – risk is increased 10 times
- Mothers who have been shown to carry GBS in this pregnancy or GBS has been found in the urine at any time during this pregnancy – risk is increased 4 times
As well as the two risk factors shown above, the following clinical risk factors also increase the chance of a baby developing a GBS infection
- Labour starts or membranes rupture before 37 weeks of pregnancy is completed (i.e. preterm) – risk is increased 3 times
- Where the waters break more than 18 hours before delivery – risk is increased 3 times
- Where the mother has a raised temperature* during labour of 37.8°C or higher – risk is increased 3 times
*If a woman has an epidural, a slightly raised temperature may be of less significance than in a woman with no epidural.
Carrying GBS, combined with one or more clinical risk factor, increases the risk at least 12 times.
In the UK, approximately 3 out of every 4 GBS infections in babies aged 0-6 days and 9 out of every 10 resulting deaths follow deliveries where one or more of these risk factors is present.
About half of the babies born to mothers colonised with GBS at the time of delivery will become colonised themselves and, of these, even without preventative antibiotics in labour, only around 1 in 200 will develop GBS disease. Carrying GBS during labour and delivery does not mean necessarily that you or your baby will become ill.