1 in 5 pregnant women carry Group B Strep, and most never know. Here's what it is, why the NHS doesn't screen for it, and what to do if you're concerned.
Group B Streptococcus (GBS) is a bacteria that lives naturally in the gut and vagina of around 20–25% of women in the UK. It causes no symptoms and is not an infection — it's part of normal bacterial flora. Most women who carry it will never know.
The reason it matters in pregnancy: GBS can be passed to the baby during labour and birth. In most cases nothing happens. But in a small number of cases it causes early-onset GBS disease in newborns — a serious condition that is preventable.
Unlike many other countries, the NHS does not offer routine GBS swab testing in pregnancy. The rationale is that carriers change — a negative swab at 34 weeks doesn't guarantee negative at 40 weeks — and that blanket intravenous antibiotic treatment in labour carries its own risks.
Many parents (and clinicians) disagree with this approach. You can request a GBS test privately — a vaginal and rectal swab at 35–37 weeks. The charity Group B Strep Support (gbss.org.uk) provides test kits. If you test positive, you are entitled to discuss intrapartum antibiotic prophylaxis (IAP) — antibiotics during labour — with your midwife.
Even without a positive swab, the NHS offers intrapartum antibiotics if any of these risk factors are present:
• GBS found in urine during this pregnancy (indicates heavy colonisation)
• You had a previous baby who developed GBS disease
• You develop a fever in labour
• Your membranes rupture more than 18 hours before delivery
• Labour begins before 37 weeks
If any of these apply to you, tell your midwife explicitly when you arrive in labour. Don't assume they'll spot it in your notes in a busy triage environment.
Around 340 babies in the UK develop early-onset GBS disease each year — out of roughly 600,000 births. Most babies exposed to GBS are completely unaffected. But because the condition can deteriorate rapidly, knowing the signs is important for every parent in the newborn period.
Signs in the first 24–48 hours that need immediate attention: grunting or fast breathing, poor feeding or not waking for feeds, a temperature above 38°C or below 36°C, being floppy or unusually pale or mottled skin. These are not specific to GBS — they're the general signs of a sick newborn — but they need same-day assessment regardless of cause.
GBS is an area where the evidence is genuinely contested, NHS policy is not universally agreed upon, and individual circumstances vary significantly. You are entitled to an informed conversation with your midwife or obstetrician about your personal risk profile, the pros and cons of private testing, and your options for intrapartum management.
The RCOG (Royal College of Obstetricians and Gynaecologists) has a patient leaflet on GBS that is worth reading before that conversation — it covers the evidence clearly and without alarmism. The Group B Strep Support charity is also an excellent resource and runs a helpline.