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Patient information

Group B Streptococcus (GBS) 

Group B Streptococcus (GBS) is the most common cause of life-threatening infections in newborn babies in the UK.  TDL provide a service to test for GBS that can be done in the comfort of your own home.

What is Group B Streptococcus (GBS)?

Group B Streptococcus is a naturally occurring bacterium carried by 20-40% of adults, usually without any symptoms or side-effects. It is commonly found in the gut and for up to 25% of women in the vagina. Carrying GBS does not present any symptoms in itself.

It can cause an infection in young babies during pregnancy and labour that can lead to sepsis and meningitis. GBS is not a sexually transmitted disease and having treatment does not stop you getting the bacterium again in the future.

Most GBS infections can be prevented by giving antibiotics intravenously (through a vein) at the onset of labour to all women who carry GBS. UK guidelines recommend mums should be offered these antibiotics in labour:

  • if GBS has been detected during the current or previous pregnancy
  • if a previous baby had GBS infection
  • if she is in preterm labour (before 37 completed weeks of pregnancy) or
  • if she has a fever in labour.

Another risk factor is waters breaking more than 18 hours before birth.  

Intravenous antibiotics in labour are highly effective at preventing GBS infection in newborn babies, reducing the risk for a newborn baby born to a woman carrying GBS from around 1 in 400 to around 1 in 5000. Oral antibiotics should not be given during pregnancy for GBS as they have not been shown to reduce GBS infection in babies.  

There are always small but potentially serious risks associated with taking antibiotics, and this needs to be fully discussed with your doctor or midwife.


Visit the TDL GBS website to order a test online.

Screening for GBS is not routinely offered in the NHS. Laboratory testing for GBS is routinely undertaken at The Doctors Laboratory following the method described in the UK Standards for Microbiological Investigations, using enriched culture medium (ECM). 

Two swabs (lower vaginal and rectal) need to be cultured, ideally in the last five weeks of pregnancy, to best predict GBS carriage around the time of delivery.

When the ECM test is properly performed within 5 weeks of giving birth, a negative result was shown to be 96% predictive of not carrying GBS at delivery (4% of women acquired carriage between the test and birth) and a positive result 87% predictive of carrying GBS at delivery (13% of women lost carriage in that time). The test can be performed earlier, but isn’t as reliable at predicting carriage status over longer periods. It can be performed later, although the chance of the baby arriving before the result increases.

Testing for GBS needs to be included in the pregnancy and birth plan and discussed with the midwife, obstetrician or GP including the treatment plan if GBS is detected. UK guidelines recommend that, when GBS is detected during the current pregnancy, the woman should be offered intravenous antibiotics in labour. This will stop most GBS infections from developing in newborn babies.

Antibiotics may affect the GBS test result. If you are taking antibiotics, or have recently, discuss this with your midwife or doctor.

GBS carriage can come and go, though tests are very predictive for a period of 5 weeks or so. Testing is usually undertaken after 35 weeks of pregnancy. Two swabs need to be taken and sent to the designated testing laboratory the same day by Royal Mail Tracked 24 postage; delays in sending can affect the result. The swabs should be accompanied by a completed request form showing:

  • Patient’s name, address, date of birth and date sample taken. Please provide the address to where results are to be sent.
  • Mobile phone number for you to receive results by text message.
  • Name, full address, phone and email address of the healthcare professional to whom positive results will be sent.

The result of the test will be normally available within 3-5 working days of receipt by The Doctors Laboratory of the swabs. Results will be sent to the patient and if positive to the named healthcare professional indicating whether GBS has been isolated (positive) or not (not-isolated).

The cost is £37.50 for the test (Delivery charge: £0.00).

The test kit can only be delivered within the UK. Once payment has been made you will receive an order acknowledgement by email, and an email confirming your payment. A further email will confirm when your kit is being readied for despatch.

The GBS testing service includes a self-collection kit.


Group B Strep Support

Tel: 0330 120 0796  E-mail:  Website:

Group B Strep Support  is a UK charity providing accurate and up to date information on GBS for families and health professionals. Group B Strep Support endorses the availability of reliable prenatal testing and wants ECM testing to be available to all pregnant women through the NHS. The charity’s current leaflets are available from their website at or by post.

Registered charity No 1112065

If you are pregnant and want more information about Group B Strep, visit


UK Standards for Microbial Investigations (SMI) B 28: investigation of genital tract and associated specimens.

UK Standards for Microbial Investigations (SMI) B 58: detection of carriage of group B streptococci.

Prevention of Early-onset Neonatal Group B Streptococcal Disease. Hughes RG, Brocklehurst P, Steer PJ, Heath P, Stenson BM on behalf of the Royal College of Obstetricians and Gynaecologists. Prevention of early-onset neonatal group B streptococcal disease. Green-top Guideline No. 36. BJOG 2017;124:e280–e305.