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Innermost Secrets / Innermost Living / Body Clock
Skip Navigation LinksGroup B Streptococcus
Page modified at: 23/01/2012
Since the 1970s, group B streptococcus (GBS) has been recognised as the primary cause of bacterial infection in newborn babies, resulting in disease at birth and up to 3 months of age.

Around a third of all men and women carry GBS in their intestines without symptoms and roughly a quarter of women of childbearing age carry GBS in the vagina at any one time. GBS is a normal body commensal (an organism that lives on another without harming it).
 A positive swab result for GBS means a woman is colonised with GBS at the time the swab was taken - not that she or her baby will become ill.
GBS colonisation is normal and does not require treatment with antibiotics. The time when antibiotics are effective against GBS infection in newborn babies is when they are given intravenously to a pregnant woman when she goes into labour or her waters break. If GBS is found in the urine, this should be treated at the time of diagnosis with oral antibiotics and the treatment repeated if necessary until urine tests come back clear. This is also an indication that the pregnant woman should be offered intravenous antibiotics once labour starts or her waters break.


A low vaginal swab and rectal swab are taken and sent for conventional culture and a new sensitive test using a special ennriched culture medium (ECM) which is even more sensitive. Most hosptals and clinics do not use this ECM and the their pick up rate is lower.

Group B strep can infect the blood. It can also cause inflammation of the baby’s lungs, brain, or spinal cord.

Long-term effects can include blindness, deafness, mental retardation, or cerebral palsy.

In rare cases, infection causes death. Infection is most often detected soon after the baby is born.


Group B strep often lives in the vagina or rectum. If the amniotic sac breaks early, bacteria from the vagina can travel to the uterus, reaching the baby. Or, as the baby passes through the birth canal, it can come in contact with the bacteria. In rare cases, group B strep can also be passed to the baby after delivery. The source of this type of infection is not well understood.


Medical research shows the prevention measures described in these pages stop GBS infections developing in babies in at least 8 out of every 10 cases - this saves lives!
Waiting to give antibiotics to the baby after delivery will sometimes be too late. Clinical randomised medical trials have proven that most early-onset GBS infection can be prevented by giving intravenous antibiotics in labour through until delivery to women whose babies are at increased risk. Research shows intravenous antibiotics take between 2 and 3 hours to cross the placenta and reach therapeutic levels in the baby, although lesser times have proved beneficial: something is better than nothing.

Babies who develop GBS infection can require long stays in hospital and expensive supportive treatment. Prevention strategies for GBS infection are cost-effective - not only can consistent prevention strategies stop babies becoming ill and dying from GBS infection, they can save money too.

To stop as many cases of GBS infection in newborn babies as possible, women with any risk factor would need to be given intravenous antibiotics during labour for ideally at least four hours before delivery.

Some women will prefer not to receive antibiotics if their risk is only slightly increased since it would inevitably complicate an otherwise natural birth, plus antibiotic therapy is associated with rare but significant complications.  The risk of a GBS infection in the baby must be balanced against the wishes and beliefs of the woman in labour and against her risk of an adverse reaction to the antibiotics.

Medical research shows the chance of a baby developing early-onset GBS infection can be reduced by over 70% (and the number of deaths by 75-80%) by adopting the following measures.




1) women at increased risk should be offered antibiotics immediately at the onset of labour or rupture of membranes (this includes women known to carry the GBS bacteria where no other risk factors are present, and women not known to carry the GBS bacteria but who have another risk factor present

2) women at particularly high risk should be strongly advised to accept intravenous antibiotics immediately at the onset of labour or rupture of membranes until delivery (this includes women who are known GBS carriers with one or more clinical risk factors and women who have previously had a baby infected with GBS, regardless of other risk factors. It also includes women who are not known to be GBS carriers but who have multiple risk factors).

3) for women in labour, the recommended doses of penicillin G are 3 g (or 5 mU) intravenously initially and then 1.5 g (or 2.5 mU) at four hourly intervals until delivery. For women who are allergic to penicillin, the recommended doses of clindamycin are 900 mg intravenously every 8 hours until delivery. Intravenous antibiotics should be given for at least 4 hours prior to delivery where possible.

4) babies born in situations where there is increased risk and the mother has received at least four hours of intravenous antibiotics should be assessed carefully by a paediatrician and, if completely healthy, intravenous antibiotics should not be given to them (see paediatric prevention).

5) babies born in a higher risk situation where the mother has not received at least four hours of intravenous antibiotics should be investigated and initially commenced on antibiotics until it has been proven the baby is not infected.