GBS (Group B Streptococcus)
What is GBS?
GBS is the acronym commonly used for Group B Streptococcus or gram B streptococcus.
GBS is a normal bacteria found within the vagina and anus areas. Approximately 20% (1 in 5) of women will have GBS colonised at any given time. This is a transient bacteria and commonly has a life cycle of 5 weeks, meaning you can have it one day & not the next. You will most likely be asymptomatic even if you test positive to GBS.
How is the test done for GBS?
Your care provider will more than likely offer you a GBS test around 35-36 weeks gestation. Mostly, you will be offered to do the swab yourself. If you agree to having the test done, you will be instructed to insert the tip of the swab just inside the vagina and sweep out it out passed the anus.
Why might you want to have this test?
GBS can cause a very serious infection in a newborn that can be passed through the vaginal passage. If the baby picks up some of the GBS there is a risk that the babies immune system won’t be ready for the bacteria and can get sepsis (whole body infection), resulting in a very sick baby.
What if I test positive?
The normal course of action is prophylactic antibiotics (usually penicillin) given to you once you are in established labour (or if your waters break, therefore allowing the bacteria to crawl up into the uterus). The Antibiotics cross the placenta and give the newborn antibiotic cover in those first few days of life to help fight off the bacteria.
Whats the risk of my baby getting sick?
There is a 20%/1in 5 chance of being GBS positive at birth.
Of those positive, the baby has a 1 in 200 chance or 0.5% chance of severe sepsis, if no prophylactic antibiotics are given. (reference ).
There are signs of infection that we can look for in the newborn-an increase in temperature is the biggest indicator of infection. Within most hospitals babies of mothers that test positive have their temperature checked every 4 hours for 24-48 hours hours after birth.
If a baby does become septic, intravenous antibiotics will be required and admission to the special care nursery.
Why might I decline this test?
There is some evidence that prophylactic antibiotics are an unnecessary risk to both the mother and a neonate. Some practitioners believe the relative risk of infection is not comparable to gross exposure to antibiotics. Antibiotics do change the flora of the gut for both mother and baby. Again, antibiotics are magnificent drugs that have helped saved many lives, but with everything there are pros and cons.
Some women, have the test and if positive have the antibiotics, have the test and if positive decline antibiotics but keep a close on on signs and symptoms of their baby once born, decline the test and monitor their baby closely in the 24-48 hours post birth. Some women believe that this is not a cause for concern.
Interestingly, in here in Australia some states, and some other countries, are now not recommending routine GBS testing, rather only testing those in high risk categories. Here in Victoria, GBS screening is still considered routine pregnancy care.
References-
https://evidencebasedbirth.com/groupbstrep/
https://ranzcog.edu.au/womens-health/patient-information-resources/group-b-streptococcus
https://www.cochranelibrary.com/central/doi/10.1002/central/CN-01007525/related-content