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Pregnancy, Group B Streptococcus + Probiotics

Co-authored by Felicity Harvie.

What is Group B Streptococcus?

Group B Streptococcus (GBS) is a common bacterium that is generally found in the gastrointestinal tract, vagina, and urethra. The bacteria can be passed from mother to baby during the birthing process and can lead to infection in the first week of baby’s life (1).

GBS is considered to be a major cause of primary neonatal sepsis, pneumonia and meningitis in the first week of a newborn baby’s life. There conditions are known to be caused by early-onset GBS infection (1)

In Australia, GBS is routinely tested for in most hospitals at around 35-37 weeks’ gestation. The main way of screening pregnant women for GBS is with a vaginal swab.

What is the treatment for Group B Streptococcus during pregnancy?

Intravenous antibiotic treatment during labour is the conventional treatment for GBS. This has been shown to prevent GBS infection in newborns with mothers who tested positive for GBS during pregnancy (2). Unfortunately, there are of course, limitations to this course of treatment.

Firstly, antibiotic treatment during labour does not prevent infection earlier in pregnancy which can lead to preterm births and stillbirths. Nor does it prevent late onset infections in newborn babies (2).

Secondly, there are also some risks in taking intravenous antibiotics for both mother and baby. These include maternal anaphylaxis, infection with other bacteria, yeast infections, increased risk of baby developing asthma and allergies and other long-term health consequences linked to alterations to the newborn microbiome (3).

So, what can I do if I test positive to Group B Streptococcus?

Studies show that taking oral probiotics containing Lactobacillus species can reduce the risk of GBS colonising the vagina of pregnant women (1).

A randomised-control trial found that oral probiotics containing Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 administered to women during early pregnancy reduced the presence of GBS in the vagina and rectum. It was concluded that early treatment with probiotics could reduce the risk of early-onset GBS infection and the need for antibiotic treatment during labour (1).

Another study gave women who tested positive for GBS an oral probiotic containing Lactobacillus salivariusCECT 9145. The women took the probiotic daily from weeks 26 to 38 of pregnancy. By week 38, 68-72% of women in the group tested negative for GBS (4).

Strain specific probiotic therapy during pregnancy could reduce the number of women who test positive for GBS during pregnancy, decreasing the number of women receiving intravenous antibiotic therapy during labour (4).

What else can I do to maintain a healthy vaginal microbiome?

What we feed our bodies prior to conception and during pregnancy can have an impact on the microbiome. Start contributing to the health of you vaginal microbes today with these simple tips:

· Eat plenty of prebiotic rich foods. Include lots of colourful fruits, vegetables, legumes, nuts and seeds in your daily diet. These foods are great sources of fibre that can feed the bugs that live in your gut, in turn, benefiting the vaginal microbiome.

· Include a source of probiotic foods in your diet daily. Include fermented dairy products such as yoghurt and kefir, sauerkraut, kimchi and kombucha. These introduce extra bacteria and yeast to your digestive tract and may also go on to benefit the vaginal microbiome.

· Smoke and drink less. Smoking and drinking alcohol can both negatively alter the vaginal microbiome. Research shows that women who smoke have fewer Lactobacillus species present in the vagina, increasing risk of infection (5).


1. Ho M, Chang YY, Chang WC, Lin HC, Wang MH, Lin WC, et al. Oral Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 to reduce Group B Streptococcus colonization in pregnant women: A randomized controlled trial. Taiwan J Obstet Gynecol [Internet]. 2016;55(4):515–8. Available from:

2. Vornhagen J, Adams Waldorf K, Rajagopal L. Perinatal Group B Streptococcal infections: virulence factors, immunity and prevention strategies. Trends Microbiol. 2017;25(11):919–31.

3. Sharpe M, Shah V, Freire-Lizama T, Cates EC, McGrath K, David I, et al. Effectiveness of oral intake of Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 on Group B Streptococcus colonization during pregnancy: a midwifery-led double-blind randomized controlled pilot trial. J Matern Neonatal Med. 2019;7058.

4. Martín V, Cárdenas N, Ocaña S, Marín M, Arroyo R, Beltrán D, et al. Rectal and vaginal eradication of streptococcus agalactiae (Gbs) in pregnant women by using lactobacillus salivarius cect 9145, a target-specific probiotic strain. Nutrients. 2019;11(4):1–22.

5. Brotman RM, He X, Gajer P, Fadrosh D, Sharma E, Mongodin EF, et al. Association between cigarette smoking and the vaginal microbiota: A pilot study. BMC Infect Dis. 2014;14(1):1–11.

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