Approximately 15 - 20% of pregnant women are colonised with GBS.
How is GBS detected?
A swab is taken either by the woman’s health care provided or can be done by the woman between 35-37 weeks of pregnancy. If the swab is positive for GBS, the recommendation is for the mother to be given antibiotics once labour is established or the membranes have ruptured.
Penicillin is given every 4 hours intravenously, during labour using a small cannula. An alternative antibiotic is used for those allergic to penicillin. There are no benefits of taking antibiotics before labour begins.
Women found to be GBS positive at earlier gestations are treated in the same way. There is no benefit in repeating the swab later in the pregnancy.
Babies of GBS positive mothers will require observations ie. temperature, heart rate and respiratory rate before each feed for the first 24 hours. No antibiotics are usually prescribed for babies unless they are unwell.
Approximately 1 in 2000 newborn babies have Group B streptococcus bacterial infections, usually evident as respiratory disease, general sepsis, or meningitis within the first week. The baby contracts the infection from the mother during labour. There are approximately 21,000 babies are born in South Australia each year so the figure of babies affected is very low.
Australian Research – Queensland University of Technology
2006, by Karen Leigh Taylor ... A study of group B streptococcus in Brisbane : the epidemiology, detection by PCR assay and serovar prevalence. Masters by Research thesis, Queensland University of Technology.
This research found that a neonate is still at risk of acquiring Group B Streptococcus (GBS) infection upon their birth even with the implementation of early onset GBS neonatal disease preventative protocols.
Study on 374 women residing in Brisbane Australia, attending public medical providers : overall GBS prevalence was 98/374 (26.2%), a higher rate than previously reported in Australia,
This study recruited 374 women of childbearing age attending public medical providers and found an overall GBS prevalence of 98/374 (26.2%) for these Brisbane women, a rate higher than previously reported in Australia. When the GBS prevalence for pregnant women (25.6%) was compared to non pregnant women (27.2%) they were similar.
Extract from The Cochrane Report : Antibiotics given during labour for known maternal Group B streptococcal colonization
Giving a mother intravenous antibiotics during labour causes bacterial counts to fall rapidly, which suggests possible benefits but pregnant women need to be screened. Many countries have guidelines on screening for GBS in pregnancy and treatment with antibiotics.
Some of the risk factors for an affected baby are:
- preterm and low birth weight;
- prolonged labour;
- prolonged rupture of the membranes (more than 12 hours);
- severe changes in foetal heart rate during the first stage of labour; and
- gestational diabetes.
Very few of the women in labour who are GBS positive give birth to babies who are infected with GBS and antibiotics can have harmful effects such as:
- severe maternal allergic reactions;
- increase in drug-resistant organisms and exposure of newborn infants to resistant bacteria; and
- postnatal maternal and neonatal yeast infections.
The Cochrane review found that giving antibiotics is not supported by conclusive evidence. The review identified four trials involving 852 GBS positive women. Three trials, which were around 20 years old, compared ampicillin or penicillin to no treatment and found no clear differences in newborn deaths although the occurrence of early GBS infection in the newborn was reduced with antibiotics. The antibiotics ampicillin and penicillin were no different from each other in one trial with 352 GBS positive women. All cases of perinatal GBS infections are unlikely to be prevented even if an effective vaccine is developed.
Want more information the whole report can be found on Cochrane database