What is GBS?
Group B Streptococcus is one of the many bacteria that normally colonise the vagina and is present in approximately 15-30% of women. It may be passed from the mother to her baby, usually just before or during labour. If this happens, it occasionally causes a severe illness in newborns, known as early-onset GBS disease. Further information.

How does GBS affect the mother?
GBS carriage is a normal commensal in 15-30% of women and does not normally cause any symptoms, or infectious disease in those who carry the bacterium. GBS can be a cause of urinary tract infection or result in neonatal disease.

How does GBS infection affect babies?
Approximately one half of women who carry GBS will pass the bacterium onto the baby during the course of labour and delivery. Of those babies who are colonised during labour, less than 1% develop early-onset GBS disease.

Most babies with GBS infection show symptoms at birth; they may be floppy and unresponsive and may not feed well. Other symptoms may include grunting, high or low temperature, irritability, hypotension, hypoglycaemia and other signs of sepsis.

The most common GBS infections are septicaemia, pneumonia or meningitis. Further information.

What antibiotics are necessary to treat a woman who is incidentally found to have GBS on a vaginal swab during pregnancy?
She does not need antibiotics during the antenatal period, as treatment during this time does not reliably result in eradication of the bacterium from the vagina at the time of delivery. GBS does not typically cause vaginal symptoms. It is important to inform the woman of her carrier status and to record this information in her antenatal notes so appropriate action may be taken at the time of delivery. During labour, intravenous antibiotic prophylaxis should be discussed. Further information.

If a woman is found to have a GBS urine infection, what needs to be done?
Whether the woman has urinary symptoms or not, treatment with appropriate antibiotics is recommended if bacteriuria is confirmed. The presence of GBS in the urinary tract may indicate a higher level of genital tract carriage and represents a greater risk of early-onset GBS disease. Intrapartum antibiotic prophylaxis should be offered.

What should I advise a woman who requests testing for GBS?
Routine screening for GBS carriage is not currently recommended. This issue has been considered and is currently endorsed by the NHS National Screening Committee, Royal College of Obstetricians and Gynaecologists and National Institute for Clinical Excellence (NICE). If a clinician agrees to testing for GBS carriage, the optimum method is a combined low vaginal/rectal swab at 35-37 weeks, cultured in enriched medium. Further information.

One of the women I have seen in antenatal clinic is anxious because her sister’s baby had GBS disease. Does GBS carriage run in families?
There is no evidence that GBS infections or carriage have a familial tendency and the risk of early-onset GBS disease is no greater than usual.

What is the recommended course of action for a women with known GBS carriage who wishes to deliver at home or in a low risk midwifery-led unit?
It is necessary to discuss the increased risk of early-onset GBS disease in the babies of women who are known GBS carriers. It may be appropriate to repeat the test between 35 and 37 weeks gestation if the inital swab was before this time. If GBS carriage is confirmed, the recommended intrapartum antibiotic prophylaxis regime requires the use of intravenous therapy. Delivery at home or in the MLU may therefore not be an option and some women will elect to deliver in a consultant unit. There is limited evidence that intramuscular antibiotics administered during labour may provide some protection and this is an option for those who choose to deliver in the community. Further information.