Group B Strep

Group B Strep (GBS) is a common bacterium (bug) which is carried in the vagina and rectum of 2 - 4 in 10 women (20 – 40%) in the UK. GBS is not a sexually transmitted disease and most women carrying GBS will have no symptoms. Carrying GBS is not harmful to you, but it can affect your baby around the time of birth. GBS can occasionally cause serious infection in newborn babies and, very rarely, during pregnancy and before labour.

Many babies come into contact with GBS during labour or around birth. The vast majority of these babies will not become ill. However, if you carry GBS, there is a small chance that your baby will develop GBS infection and become seriously ill, or even die.

Infection is more likely to happen if: 

  • your baby is born preterm (before 37 completed weeks of pregnancy) – the earlier your baby is born, the greater the risk
  • you have previously had a baby affected by GBS infection
  • you have had a high temperature or other signs of infection during labour
  • you have had any positive urine or swab test for GBS in this pregnancy
  • your waters have broken more than 24 hours before your baby is born.

If you have had a GBS-positive swab or urine test in this pregnancy you will be offered antibiotics through a drip in labour to reduce the chance of infection. You will also be offered antibiotics if you have previously had a baby who was diagnosed with GBS infection.

If you have had GBS previously, some hospitals offer a specific test (enriched culture medium) to see whether you are carrying GBS again. If this test is not available in your local hospital, you will be offered antibiotics in labour instead. Please ask your midwife for more information.

You should discuss your planned place of birth with your midwife during pregnancy to make sure that you can receive antibiotics as required in labour. If you choose to have antibiotics, it may not be possible to arrange this at home or in some midwifery led units. Please ask your midwife for more information.

Further information is available here about GBS.

Research and GBS

Are you pregnant? Would you like to help researchers understand more about how the Group B Streptococcus (GBS) vaccine protects babies? 

We are researching a GBS vaccine to see if this provides an effective level of antibodies to infants to best protect them from GBS infection. This will help provide key data and vital information, as no GBS vaccine is currently available for clinical use. 

We are inviting pregnant women who do not have any complications in their pregnancy to take part in this study. In this study, women will be assigned randomly (by chance, like flipping a coin) to 1 of 5 groups and receive 3 injections (each 4 weeks apart). Participants will receive either the GBS vaccine or a placebo so researchers can tell if the effects seen in the study are a result of the vaccine or not. 

Participation includes: 

- study visits throughout pregnancy and up to 6 months after delivery 

- a 24-hour phoneline to the study team 

- travel reimbursement for study visits 

- completion of an e-diary to record any symptoms following vaccination.

There will be eight routine study visits in pregnancy and participants will be followed up until 6 months after their baby’s birth. Blood samples will be taken from participants throughout the study and a baby blood sample will be taken when babies are 1 and 3 months old. 

To find out more please contact the Reproductive Health Research Team at the Princess Anne Hospital Southampton on 02381 206856 or


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