Group B Strep test explained

Towards the end of pregnancy you may be offered a test for Group B Streptococcus — usually shortened to Group B Strep or GBS. It’s a common thing to be screened for, and while the name sounds alarming, it’s very manageable, so here’s what it’s about.

What GBS is. Group B Strep is a common bacterium that lives harmlessly in the body — in the vagina or bowel — of a large proportion of healthy adults, often without you ever knowing. It comes and goes, and having it doesn’t mean you’re unwell or unclean; it’s just part of the normal mix of bacteria many people carry. It’s not a sexually transmitted infection.

Why it matters in pregnancy. The reason it’s screened for is that, occasionally, a baby can pick up GBS from the mother during a vaginal birth, and a small number of those babies become seriously unwell in the early days. It’s uncommon — but because it can be serious, and because it’s easily prevented, it’s worth identifying.

The test. In many parts of Australia, you’ll be offered a GBS swab at around 35 to 37 weeks. It’s a simple, quick swab of the lower vagina and around the anus (you can often do it yourself if you prefer), sent to the lab to see whether GBS is present. Some hospitals use a different approach — treating based on risk factors rather than routine swabbing (for example, if you have a fever in labour, your waters have been broken a long time, or you’ve had a GBS-affected baby before). Your care team will tell you which approach they use.

What happens if you test positive. A positive result simply means GBS was detected — it doesn’t mean anything is wrong with you or your baby, and it’s common. It means that during labour you’ll be offered antibiotics through a drip, ideally started a few hours before the birth. This dramatically reduces the already-small chance of your baby becoming unwell. The antibiotics are given in labour (not earlier), because GBS can come and go, so treating it during birth is what protects your baby.

What this means for your birth plan. Testing positive doesn’t change most of your plans — you can still usually move around, use most forms of pain relief, and have the birth you’re hoping for; you’ll just have a cannula (drip) for the antibiotics. If you’re planning a home birth or a very quick trip to hospital, it’s worth discussing the timing of antibiotics with your midwife in advance. After the birth, your baby may be watched a little more closely for signs of infection, especially if there wasn’t time for the full course.

Signs to watch in your newborn. Whether or not you tested positive, it’s always worth knowing the signs a newborn is unwell — poor feeding, being unusually floppy or drowsy, a high or low temperature, fast or grunting breathing, or just seeming “not right” — and seeking help straight away if you’re worried (call your midwife, or 000 in an emergency).

A couple of specifics come up often. If GBS is found in your urine at any point in pregnancy, or you’ve had a baby affected by GBS before, you’ll usually be recommended antibiotics in labour regardless of a swab result. And while you might read about “natural” ways to reduce GBS, there’s no proven method to reliably clear it, so the recommended approach remains antibiotics in labour if you’re positive or higher-risk. If you have a penicillin allergy, let your team know, as an alternative antibiotic can be used.

The takeaway: a positive GBS result is common and not a cause for alarm. It simply flags that antibiotics in labour are recommended to keep your baby safe — a simple, effective step. Your midwife or doctor will explain your hospital’s approach and answer any questions.