Group B Strep Testing: What It Means and What Happens if You Test Positive

Group B Streptococcus (GBS) is a common bacteria that around 1 in 5 people carry in their vagina or digestive system, usually without any symptoms and with no effect on their own health. It only becomes a consideration in pregnancy because, rarely, it can pass to a baby during labour and cause infection.

Why routine testing isn't offered to everyone in the UK

Unlike some countries, the UK does not currently offer universal GBS testing to all pregnant women as standard NHS practice, a position based on evidence that routine testing hasn't been shown to reliably reduce the (already low) rate of newborn infection, partly because carrier status can change between testing and birth. This differs from countries like the US, which is a common source of confusion for parents who've read about GBS from international sources.

When testing does happen

You may be tested if GBS is found incidentally (for example, in a urine sample taken for another reason), if you've had a previous baby affected by GBS infection, or if you specifically request testing — a private test is available if you want one and it isn't offered as routine at your trust. Some individual maternity units also test in specific circumstances, such as premature labour.

What a positive result changes

If you're known to carry GBS, or have specific risk factors (premature labour, a fever during labour, waters broken for a long time before birth), you'll usually be offered IV antibiotics during labour, given as soon as possible after labour starts and repeated every few hours until birth. This significantly reduces the already-small risk of the infection passing to your baby, which is the entire purpose of identifying carriers in the first place.

What it doesn't mean

• It doesn't mean you're unwell or unclean — GBS carriage is extremely common and unrelated to hygiene.
• It doesn't usually change your birth plan otherwise — vaginal birth remains the norm; antibiotics during labour is generally the only adjustment.
• It doesn't require treatment before labour — antibiotics given in advance of labour don't reliably clear GBS by the time you give birth, so treatment is timed to labour itself, not to the point of diagnosis.

Signs of GBS infection in a newborn

Rarely, if infection does develop, signs in the first hours or days include grunting, poor feeding, floppiness, unusually high or low temperature, or unusually fast or slow breathing or heart rate. Hospital staff monitor newborns for these signs particularly closely if the mother was a known GBS carrier, and any concerns should be raised with a midwife or doctor immediately regardless of GBS status.