Group B Strep Screening

Group B Strep screening - GBS3 Trial in UK

This landmark NIHR-funded clinical GBS3 trial aims to improve the diagnosis and treatment of GBS infection in new-born babies. The UK is one of the few countries in the developed world where there is currently no standard Group B Strep test screening programme for pregnant women and yet it is the leading cause of infection in new-borns.

This clinical trial will test two types of screening compared to no screening. The results will hopefully transform the future GBS pregnancy screening policy in the UK.

Group B Streptococcus (GBS) is a bacterium commonly found in the vagina and lower gut of approximately 1 in 4 pregnant women. GBS can come and go throughout pregnancy and for the mother there are usually no GBS symptoms and causes little or no harm but it can be passed to the baby around birth.

Hands together Group B Strep Test UK

Approximately one baby in every 1750 will develop a GBS infection within 7 days of birth.

Most babies will recover but it causes a range of serious infections including pneumonia, meningitis, and septicaemia (blood infection) and is especially dangerous to those babies born prematurely.


1 in 19 of the babies who develop a GBS infection will die from an early-onset GBS infection and 1 in 13 from a late-onset GBS infection. 1 in 14 of those who survive their GBS infection will have a long-term disability following their early-onset GBS infection and 1 in 8 following their late-onset GBS infection.

Group B Strep infection in babies can be prevented by giving intravenous antibiotics to women during labour. There are concerns that routine GBS testing could lead to large numbers of women being given antibiotics unnecessarily and the longer-term effects of antibiotics on mother and baby. Widespread use of antibiotics can also contribute to antimicrobial resistance in the general population. The current UK practice is to offer antibiotics when the baby is thought to be at higher risk of developing the infection: if the birth is preterm, if GBS was detected during the current pregnancy, if the woman has a fever or previously had an infected baby. This process is not very accurate and previous UK research has found that:

65% of babies who develop Group B Strep infections have mothers who have no risk factors for carrying the bacteria

70% of women who do have risk factors do not actually harbour the bacteria and are therefore given antibiotics unnecessarily.

Some women who are found to have Group B Strep during pregnancy may not have the infection by the time they give birth. The GBS3 trial aims to clarify these uncertainties by comparing the current standard risk factor treatment with:

a) using a lab culture GBS test to check women at 35 weeks of pregnancy (3-5 weeks before their due date).

b) a new rapid ‘bedside GBS test’ at the start of labour.

Here at Strepelle we use the Enriched Culture Medium test which is recognised as the gold standard for detecting GBS carriage.

The Aim of this Research into Group B Strep Screening

is to establish whether routine Group B Strep test screening of women (in late pregnancy or during labour) and subsequent treatment with intravenous antibiotics, is better at reducing GBS infection than using the current risk factor approach and if it represents value for money for the NHS

The trial is in the planning stages to be ready as soon as Covid19 allows and will involve 80 hospitals and birth centres in England and Wales. They will be randomly allocated the risk factor or the routine GBS testing approach. Hospitals allocated to the routine testing approach will also be randomly divided into testing women using a swab taken from the vagina and rectum either at

Pregnancy essentials, Strep b private test UK
a) at 35-37 weeks of pregnancy, using a lab-based Group B Strep test or b) in labour, using a rapid bedside test machine.

Women with a GBS positive test result will be offered antibiotics in labour. All mothers in preterm labour or who had a previous baby with GBS infection will be offered antibiotics as per current guidance.

The Trial will compare the number of babies who develop serious infection in all routine testing hospitals and birth centres with those using the risk factor approach. As infections are relatively rare, the trial needs to collect information on 320,000 women to be able to see a difference between the two main approaches. The allocated testing strategy will be adopted as standard practice by the units involved. The trial is being led by Dr Kate Walker and Dr Jane Daniels, Clinical Assistant Professor of Obstetrics and Professor of Clinical Trials at the University of Nottingham School of Medicine.

Further information and updates available