Probiotics & Group B Strep (GBS) in Pregnancy

Group B Streptococcus (GBS) is a common bacterium found in the gastrointestinal tract, urinary tract, and reproductive system. This bacteria is transient, meaning it can come and go from our bodies without causing issues.

However, in pregnancy, GBS can be more serious. Around 1 in 4 women carry GBS, and during pregnancy it can cause infections in the urinary tract, placenta, uterus, and amniotic fluid. Even without symptoms, GBS can be passed to your baby during labour and delivery, which is why awareness and testing are so important.

GBS Testing During Pregnancy

In Australia, pregnant women are routinely screened for Group B Strep between 35-37 weeks gestation.

• The test involves a simple vaginal swab collected by your healthcare provider.
• Results usually return within 48 hours and will be either positive or negative for GBS.

If your result is negative, no treatment is needed. If positive, you’ll likely be given intravenous antibiotics during labour to reduce the risk of passing GBS to your baby. Penicillin is the most common choice.

Why GBS Matters for Newborns

Premature babies are more vulnerable to GBS infection than full-term babies because their immune systems are less developed. Risks include:

• Colonisation: About 50% of babies born to untreated, GBS-positive mothers become colonised with the bacteria.
• Early-onset GBS infection: This can be life-threatening, but the risk drops from 1-2% to 0.1-0.2% with antibiotics in labour.
• Severe outcomes: While rare, GBS infection can lead to meningitis, long-term health problems, or in severe cases, death.

Accuracy of the GBS Test

• Negative at 35-36 weeks: 91% remain negative at labour, but 9% test positive later.
• Positive at 35-36 weeks: 84% remain positive at labour, but 16% become negative and may receive unnecessary antibiotics.

Probiotics & GBS: Can They Help?

While antibiotics remain the standard treatment for GBS-positive women in labour, they can also disrupt the mother’s microbiome, affect breast milk’s probiotic content, and impact a newborn’s gut health.

Research is emerging on the role of probiotics in pregnancy to reduce GBS colonisation:

• Strains Lactobacillus rhamnosus and Lactobacillus reuteri may help lower GBS colonisation rates.
• A 2016 randomised trial in Taiwan found that 43% of GBS-positive women taking probiotics tested negative in labour, compared to only 14% in the placebo group.
• Lab studies show vaginal lactobacilli can inhibit GBS growth by increasing vaginal acidity.

A large clinical trial is currently underway to further understand the benefits of probiotics for GBS in pregnancy-early results are promising.

Key Takeaway: If you test positive for Group B Strep in pregnancy, follow your care provider’s guidance on antibiotics. If you want to support your microbiome, discuss probiotic supplementation - especially strains like L. rhamnosus and L. reuteri, with your healthcare professional.