I wish I knew then what I know now. In all three of my pregnancies, I was routinely tested for GBS. I really didn't know what GBS was, why I was being tested, or what my options were. During my third pregnancy, I tested GBS+ and was told I would need antibiotics so I assumed there were no other options. When I went into labour at 38 weeks, I arrived at the hospital and was immediately given an IV.
I don't regret anything, I just wish I had more information to make an informed decision.
In this blog, I will break down the research and evidence on GBS, to help you understand what it is, why and when routine tests are performed and your options.
First off, what is GBS?
GBS stands for 'Group B streptococcus' (also known as Group B strep). GBS is a common type of bacteria that live in the intestines, urinary and genital tract. It is estimated that between 10% and 30% of pregnant women carry GBS.
"GBS is passed from one person to another by skin to skin contact and can be passed on through sexual contact. However, there are no known harmful effects of carriage itself and, since the GBS bacteria do not cause genital symptoms or discomfort, GBS is not a sexually transmitted disease. Neither is GBS carriage a sign of ill health or poor hygiene."
https://www.infantjournal.co.uk/pdf/inf_012_gbs.pdf
GBS is usually not serious for adults, but it can be harmful to newborns.
How could GBS affect my baby?
In newborns, GBS can cause sepsis (infection of the blood after birth), meningitis, and pneumonia. Neonatal GBS disease can be classified as early- or late-onset. Early-onset disease occurs less than 7 days after birth and is associated with a mortality rate of 5% to 20%.
The presence of bacteria does not necessarily mean infection, and infection does not necessarily mean death. Both mother and baby could have GBS bacteria in their systems (be colonized) and show no symptoms. Infants can become very unwell when GBS causes infection – invading the bloodstream, lungs or cerebrospinal fluid
All about testing
Guidelines on routine testing differ based on where you live:
Universal approach:
In the USA and Canada, the guidelines require that all pregnant individuals are offered screening for GBS at 35 to 37 weeks’ gestation (this includes individuals with planned Caesarean delivery) and treat everyone who is positive with antibiotics during labor
Risk based approach:
In the UK, the recommendation is a 'risk-based' strategy, where pregnant individuals presenting risk factors for early-onset GBS infection are offered antibiotics in labour (GBS in the urine at any point in pregnancy, previously gave birth to an infant with early GBS infection, goes into labor at less than 37 weeks, has a fever during labor, or water has been broken for more than 18 hours). The UK guidelines state; "routine screening for group B streptococcus colonization in late pregnancy should not be introduced in the UK, as the potential harms of unnecessary treatment with antibiotics may outweigh the benefits"
Can routine testing be declined?
It can be declined, just as any other test, treatment, or intervention. Understanding the risks and considerations is important in making an informed decision. Choosing not to test would make you “GBS unknown.” Being GBS unknown can be a disadvantage if you develop risk factors in labour that increase the chances of your baby getting sick with GBS, such as a fever or prolonged rupture of membranes. In this situation, you will be offered antibiotics because you may have GBS. The benefit of testing is that it will help you avoid taking antibiotics you don’t need.
Antibiotics in labour
If the swab tests positive for GBS, mothers are treated with antibiotics in labour (most often penicillin). The CDC recommends that antibiotics be given every 4 hours, starting more than 4 hours before birth. If a pregnant person who carries GBS is not treated with antibiotics during labour, the baby’s risk of developing a serious GBS infection in the first week of life is 1% to 2%. If a GBS carrier is treated with antibiotics during labour, the risk of their baby developing early GBS disease drops to 0.2%.
One study found that 61.4% of term infants with group B streptococcal disease were born to women who had had negative cultures for group B streptococcus https://www.nejm.org/doi/full/10.1056/NEJMoa0806820
Potential benefits of antibiotics:
Decreases the risk of early GBS infection
Lowers the chances that your baby will need special testing or monitoring after they are born
Potential harms of antibiotics:
Possible allergic reaction (The risk is estimated to be 1 in 10,000 for a severe reaction, and 1 in 100,000 for a fatal reaction)
Increase risk of maternal and newborn yeast infections. In one study, 15% of women who received antibiotics in labour had mother-baby yeast infections, compared to 7% of mothers who did not have antibiotics
Potential medicalization of labor and birth
Potentially altering the infant microbiome
Research suggests that there is increasing concern that unnecessary use of antibiotics increases the risk of infections with resistant bacteria. There is also some speculation that antibiotics may bring about changes in the baby’s immune system as a result of changing the organisms living in the baby’s gut. Giving antibiotics may, therefore, be useful in the short term, but in the long term may bring about different problems.
How do I decide what's best for me and my baby?
There is no 'right' or 'wrong' choice when deciding what's best for you. It's important to make an informed decision based on the benefits, risks and alternatives to testing and antibiotic treatment in labour.
Here are some questions you can ask yourself when making a decision:
Do I understand the benefits and considerations of declining vs testing for GBS and how this can affect my labour?
Do I understand how treating or not treating with antibiotics can impact my labour and my baby?
How do I feel about having or avoiding antibiotics?
How important is it to avoid IV during labour? If it's important, have I explored ways to make this a more comfortable experience with my care provider?
Do I understand the benefits vs risks of taking antibiotics vs declining
Citing and additional reading
Gyllensvärd J, Studahl M, Gustavsson L, et al. Antibiotic Use in Late Preterm and Full-Term Newborns. JAMA Netw Open. 2024;7(3):e243362. doi:10.1001/jamanetworkopen.2024.3362
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