Group B streptococcus (GBS) is a common bacterium that lives harmlessly in the gut, vagina and rectum of many healthy women. Carrying it is called being “colonised” — it is not a sexually transmitted infection and is not a sign of poor hygiene, and it usually causes no symptoms. It matters in pregnancy because GBS can occasionally be passed to the baby around birth and, rarely, cause a serious newborn infection. Serious GBS infection in babies is uncommon, but because it can be very serious, maternity teams take steps — chiefly antibiotics in labour — to reduce the risk.
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In a medical emergency, or for severe or sudden symptoms such as breathing difficulty, chest pain, fainting or stroke signs, call 995 immediately.
A newborn who seems unwell — poor feeding, grunting or fast breathing, an abnormal temperature, floppiness or unusual drowsiness — needs urgent medical assessment; mention any GBS concern. Call 995 if a baby is seriously unwell.
What it is and why it matters
Carrying GBS causes no symptoms and needs no treatment outside pregnancy. The concern is that around the time of birth — as the baby passes through the birth canal, or after the waters break — GBS can reach the baby and, in a small number, cause infection such as sepsis, pneumonia or meningitis in the first week of life (early-onset disease); a later form can occur up to about three months of age. To give a sense of scale, RCOG and the NHS report early-onset GBS disease affects roughly 1 in 1,750 newborns in the UK, a figure that varies by country and over time and is not a Singapore statistic.
Who is at higher risk
The baby’s risk of early-onset GBS infection is higher if GBS was found in the mother’s vagina, rectum or urine during this pregnancy, if a previous baby had GBS infection, with premature birth before 37 weeks, if the waters have been broken for a prolonged time before birth, or if the mother has a fever or signs of infection in labour. Many babies are exposed and stay well; only a small number become ill.
Symptoms
In the mother there are usually no symptoms at all, which is exactly why testing or risk assessment is used rather than relying on how she feels — though GBS can sometimes cause a urinary tract infection. In a newborn, the signs parents are told to watch for include being unusually floppy or unresponsive, poor feeding, grunting or fast or laboured breathing, a very high or low temperature, and pale or blotchy skin.
Screening and how it is assessed
Practice varies by country and hospital, so there is no single universal rule. Some settings use universal screening — a vaginal-rectal swab late in pregnancy, commonly around 35 to 37 weeks — to find carriers, while others use a risk-factor-based approach, because GBS is common, swab results can change and testing cannot reliably predict which babies will fall ill. GBS may also be picked up incidentally on a urine test during antenatal care. In Singapore, whether and how testing is offered is decided by your maternity team and hospital protocol, so ask your obstetrician or midwife what your hospital does. Care is led by the maternity team, often with your GP involved in shared antenatal care.
Treatment and protecting the baby
GBS carriage itself is not treated with antibiotics during pregnancy, because treating it earlier does not reliably clear it before birth — the exception being GBS found in the urine, which is usually treated as a UTI. The key protective step is intravenous antibiotics during labour for women who are carriers or who have relevant risk factors; given in labour, this substantially reduces the chance of the baby developing early-onset infection. This guide gives no doses — the maternity team chooses the drug and dose. If there are concerns after birth, the baby may be observed in hospital and given antibiotics if any signs of infection appear. Whether antibiotics in labour are offered, and to whom, is a shared decision based on your screening result, risk factors and hospital policy.
What this means for your birth
Carrying GBS is not, by itself, a reason for a caesarean — the usual plan is a normal vaginal birth with antibiotics through a drip during labour. It helps to discuss GBS at your antenatal visits: ask what your hospital’s testing and labour-antibiotic policy is, and tell your team if you have ever carried GBS or had a previous baby affected by it, as this affects the plan. If your waters break, you develop a fever, or you think you are in preterm labour, contact the maternity unit straight away, since these situations change how GBS is managed. After birth, keep an eye on your baby for the warning signs, including in the weeks after going home, and seek help promptly if you are worried.
When to see a doctor
Discuss GBS with your obstetrician, GP or midwife at antenatal visits, and contact your maternity unit straight away if your waters break, you develop a fever, or you think you are in preterm labour. After birth, seek urgent medical care — or call 995 in an emergency — if your baby shows any signs of being unwell.
Related pregnancy & women’s-health topics
- Hyperemesis gravidarum
- Placenta praevia
- Placental abruption
- Cholestasis of pregnancy
- Pelvic girdle pain
- Anaemia in pregnancy
- Preterm labour
- Gestational hypertension
- UTI in pregnancy
- Pre-eclampsia
- Obstetricians & gynaecologists
Sources
- RCOG — Group B Streptococcus (GBS) in pregnancy and newborn babies: rcog.org.uk
- NHS — Group B strep: nhs.uk
- CDC — Group B Strep: cdc.gov
- KK Women’s and Children’s Hospital — Conditions & Treatments: kkh.com.sg