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Group B Streptococcus (GBS)

A guide to GBS, testing during pregnancy, and protecting your baby around the time of birth.

1. What is GBS?

Group B Streptococcus (GBS) is a common type of bacteria that can live naturally in the digestive and genital tract. Many healthy adults carry GBS without knowing it and have no symptoms.
GBS is usually harmless to the mother. However, it can occasionally cause a serious infection in a newborn, particularly during the first days or weeks of life.

2. GBS during pregnancy

Being positive for GBS does not mean that you or your baby are ill.
GBS can come and go naturally, which means a test taken during one pregnancy may not accurately predict whether you will carry GBS in a future pregnancy.
If you have previously tested positive for GBS, tell your midwife, doctor, or maternity team early in your next pregnancy. Depending on your country and individual circumstances, you may be offered another test, or your previous GBS history may affect the care recommended during labour.

3. When is GBS tested?

Testing recommendations vary between countries.
Where routine screening is offered, a swab is commonly taken from the vagina and/or rectum towards the end of pregnancy, often around 35–37 weeks.
Some healthcare systems do not routinely screen every pregnant woman and instead recommend antibiotics during labour when certain risk factors or a previous history of GBS are present.
Always follow the recommendations of your local maternity service.

4. If you test positive

A positive GBS test does not usually require treatment during pregnancy because GBS can return after treatment.
In many healthcare systems, the recommended way to reduce the risk to the baby is to give the mother antibiotics through a vein during labour. These antibiotics help reduce the amount of GBS that can be passed to the baby during birth.
Your healthcare team will explain whether antibiotics during labour are recommended for you.

5. If you have had GBS before

If you have previously had a baby who developed a GBS infection, or you tested positive for GBS during a previous pregnancy, tell your maternity team at the beginning of your next pregnancy.
You can ask your healthcare professional whether repeat testing is recommended in your country and whether your previous GBS history means you should receive antibiotics during labour.

6. After birth

Most babies born to mothers who carry GBS remain completely well.
Healthcare professionals may monitor your baby more closely after birth if there are concerns about GBS or other risk factors.
Seek urgent medical attention if your newborn develops signs of illness, including: difficulty breathing or breathing very fast.
Blue, pale, or unusually mottled skin.
Being unusually sleepy, difficult to wake, floppy, or unresponsive.
Feeding poorly or refusing feeds.
A temperature that is unusually high or low.
Seizures or unusual movements.

7. Remember

GBS is common, and testing positive does not mean that you have done anything wrong. Most babies of mothers who carry GBS are healthy. Knowing your GBS status and discussing your history with your maternity team helps you understand what care may be recommended during labour and after birth.

8. Disclaimer

This information is provided for general educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. GBS screening and treatment recommendations vary between countries and individual circumstances. Always discuss your GBS history and pregnancy care with your midwife, doctor, obstetrician, or other qualified healthcare professional.

When in doubt, ask a professional

This guide is for general information only. If you're worried about your baby's health or feeding, speak with your GP, health visitor, or paediatrician.