Group B Strep in Pregnancy: Tests, Labour Antibiotics and Baby Care
Key message: Group B Streptococcus commonly lives in the bowel or vagina without symptoms. It is not a…
Key message: Group B Streptococcus commonly lives in the bowel or vagina without symptoms. It is not a sexually transmitted infection, but it can rarely cause serious early infection in a newborn, so labour antibiotics are offered when risk is increased.
Get urgent help: Contact maternity care when labour starts or waters break if GBS was found in this pregnancy or a previous baby had GBS disease. After birth, urgent newborn assessment is needed for poor feeding, abnormal temperature, grunting, fast or difficult breathing, unusual sleepiness, irritability or colour change.
What does GBS carriage mean?
Carriage is common, can come and go and usually causes no maternal illness. It does not reflect hygiene or fidelity.
A positive result at one time does not prove carriage at every later time, but results during the current pregnancy influence birth planning.
How is GBS found?
- A vaginal/rectal swab taken in a service that uses screening.
- GBS found in urine during pregnancy.
- A vaginal swab taken for another reason.
- A previous baby with early- or late-onset GBS infection.
- Testing policies vary by country; follow the current screening policy used by your maternity service.
When are antibiotics in labour offered?
Penicillin given intravenously during labour is commonly used, with an alternative chosen from the allergy history. Starting early in labour gives the greatest protective effect.
- GBS found in the current pregnancy.
- GBS bacteriuria in the current pregnancy.
- A previous baby affected by GBS disease.
- Selected unknown-status situations with preterm labour, fever or prolonged rupture according to the local protocol.
Why not take antibiotics before labour to clear GBS?
Oral or antenatal antibiotics do not reliably eradicate carriage because GBS can return. Treating a urine infection is important, but newborn prevention still relies on the labour plan.
Do not use unprescribed antibiotics or antiseptic vaginal products.
What if I have a penicillin allergy?
The exact reaction matters. Mild intolerance is different from anaphylaxis or a severe skin reaction. The team selects an alternative and may use culture sensitivity or allergy assessment.
Document the allergy clearly before labour.
What if the waters break?
Contact the maternity unit promptly. Management depends on gestation, labour, GBS result, temperature and time since rupture. At term with known GBS carriage, induction and intravenous antibiotics may be offered promptly.
PPROM follows a separate preterm infection and birth pathway.
What if a planned caesarean occurs before labour?
When caesarean occurs before labour with intact membranes, specific intrapartum GBS prophylaxis is generally not required, although routine surgical antibiotics are still given.
If labour or membrane rupture occurs first, contact the hospital immediately.
How is the baby observed?
The newborn team considers gestation, maternal fever, duration of rupture, antibiotics and clinical condition. A well baby may be observed, while symptoms require immediate examination, blood tests and antibiotics.
Late-onset GBS can occur after the first week and is not prevented fully by labour antibiotics.
Does GBS affect breastfeeding or future pregnancy?
Breastfeeding is encouraged and does not need to stop because of carriage. Record the result and any affected previous baby in future pregnancies.
A previous positive swab without an affected baby is handled according to the current pregnancy and local protocol.
Frequently asked questions
Is GBS an STI?
No. It is common bowel/vaginal bacteria and is not evidence of sexual transmission.
Does a positive swab mean the baby will be infected?
No. Most babies remain well, and labour antibiotics reduce early-onset risk.
Can I have a vaginal birth?
Yes. GBS carriage alone does not require caesarean.
Can I use a home GBS test?
Testing should use a reliable laboratory and the result should be integrated into the maternity pathway.
Do labour antibiotics prevent every GBS infection?
They greatly reduce early-onset disease but do not prevent every case or late-onset disease.
Your next step
Keep the GBS result in the pregnancy record and contact the birth hospital early in labour or when waters break. Follow the exact screening and antibiotic protocol used by your birth hospital.
Medical and content review: Dr Mohamed Abdelghany, Obstetrics & Gynecology Specialist, MRCOG (UK), MSc Obstetrics & Gynecology – Kasr Al-Ainy, Cairo University.
Last reviewed: 23 August 2026.
This information is for general education and does not replace individual medical assessment. Severe, sudden or concerning symptoms should not wait for a routine appointment.
