Group B Strep Pregnancy Complete
Group B strep in pregnancy — what it is, testing, and treatment.
Group B streptococcus (GBS) is a common type of bacteria that naturally lives in the gut and, in a significant proportion of women, the vagina too. Carrying it isn't an illness and causes no symptoms — most people never know they have it unless they're tested. The reason it's worth understanding in pregnancy is the small risk of passing it to the baby during labour.
What GBS means for you and your baby
Carrying GBS is completely harmless to you. The concern is that if it's present in the vagina during labour, there's a chance it could be passed to the baby during birth. In the vast majority of cases this causes no problems at all, but on rare occasions it can lead to a serious infection in a newborn, most commonly in the first few days of life. Babies affected by early-onset GBS infection may show signs such as poor feeding, unusual floppiness, grunting, or a high or low temperature, and it requires prompt hospital treatment.
Testing for GBS
Routine testing for GBS is not offered as standard across the UK, unlike in some other countries. This is a deliberate policy choice, based on the fact that carrying GBS fluctuates — you can test positive one week and negative the next — so a single test doesn't reliably predict your status at the time of labour. Instead, the NHS focuses on identifying and treating known risk factors during labour itself. That said, some women choose to arrange a private test (usually a swab, taken from around 35-37 weeks) if they want more certainty going into birth, and some maternity units will test if you have specific risk factors, such as GBS in a previous pregnancy or GBS found incidentally in a urine sample.
How it's managed
If you're known to carry GBS, or you have certain risk factors (such as a premature labour, a long gap between waters breaking and birth, a fever in labour, or a previous baby affected by GBS), you'll be offered intravenous antibiotics during labour. This is usually penicillin, given as soon as possible after labour starts and repeated at intervals until birth. This treatment is highly effective at reducing the risk of the baby developing an infection, and most babies born to GBS-positive mothers who receive antibiotics in labour are completely unaffected.
What to ask your midwife
- Whether your local trust offers GBS testing, and under what circumstances
- What happens if GBS is found in a routine urine or vaginal swab taken for another reason
- What the plan would be for antibiotics in labour if you're found to carry GBS
Frequently Asked Questions
Is Group B strep dangerous during pregnancy?
Carrying GBS is not dangerous for you and causes no symptoms. The small risk relates to passing it to the baby during labour, which can occasionally cause a serious infection. Antibiotics given during labour are highly effective at reducing this risk, and most babies are unaffected even when GBS is present.
Why isn't everyone tested for Group B strep on the NHS?
GBS carriage can come and go, so a test at one point in pregnancy doesn't reliably predict whether it will be present during labour. Instead, the NHS approach focuses on recognising risk factors at the time of birth and offering antibiotics where they're needed, rather than universal screening earlier in pregnancy.
What happens if I test positive for GBS?
If you're known to carry GBS, you'll be offered intravenous antibiotics once labour begins, continuing at intervals until the baby is born. This significantly lowers the chance of the baby developing an infection, and your midwifery team will also monitor your baby a little more closely after birth as a precaution.
This article is for informational purposes only and does not constitute medical advice.
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