Group B Streptococcus is a bacteria that is present in the vaginal or bowel flora in approximately 15% of women.

Most women will not have any symptoms, however GBS can be significant for women in labour.

GBS Risk factors:

  • Preterm labour
  • Maternal fever > 37.5 degrees
  • Ruptured membranes > 18 hours
  • Chorioamnionitis (infection in the amniotic fluid & membranes)
  • Previous newborn with GBS
  • GBS bacteriuria (UTI with GBS bacteria)
  • GBS positive in a previous pregnancy is linked with a greater rate of reoccurrence in the next pregnancy


What happens if you are GBS positive in pregnancy?  

  • If a woman carries GBS and it is untreated there is a 1-2% chance the baby will get a significant lung (pneumonia) or blood (septicaemia) infection with serious consequences to the baby’s health.
  • Most babies who come into contact with GBS will not suffer any ill health, but unfortunately, we cannot tell which babies will get sick and which will not.

Women who are attempting a vaginal birth will normally be screened for GBS by having a low vaginal swab at around 36 weeks gestation.  The result only takes 2 days to return.

If the result is positive, then the mother will be given intravenous penicillin in labour or when the waters break. Another antibiotic (Clindamycin) will be used if the mother is allergic to penicillin.

What happens if labour or the waters break prior to 36 weeks?

  • In these circumstances, a swab will be taken and antibiotics administered, as preterm labour has a higher association with GBS.

What happens if my labour is so quick that antibiotics are not given at least an hour before delivery?

  • The baby will have swabs from the groin and umbilicus taken and its temperature/observations monitored for 48 hours.

What about women who are having an elective Caesarean section?

  • Usually GBS swabbing is not necessary, as the baby does not come into contact with GBS during an elective Caesarean section.
  • On the rare chance of the waters breaking prior to the planned Caesarean section date then antibiotics may be given prior to the Caesarean section being performed.