Group B Strep (GBS) – Implications for Probiotic Use During Pregnancy

A Note on GBS

Streptococcus agalactiae (AKA group B strep/GBS) is considered commensal (meaning normal) vaginal microbiota in 10-25% of women. In the presence of an overgrowth during late-stage pregnancy, this species can cause sepsis, pneumonia, and sometimes meningitis, all of which are very serious concerns for a newborn.  This is why women in Canada and the US (but not all developed countries, such as the UK and NZ) are routinely tested between 35-37 weeks gestation.  According to the CDC, a pregnant woman who tests positive for group B strep bacteria and receives antibiotics during labour has a 1-in-4,000 chance of delivering a baby who will develop group B strep disease, compared to a 1-in-200 chance if she does not.  Standard medical treatment is IV antibiotics during labour (known as Intrapartum Antibiotic Prophylaxis or IAP).

We know that antibiotics used during labour, even for a short time, do have an adverse impact on the infant’s (and mother’s) microbiome. (See our blog on the Microbiome & Birth to learn why that matters.)  We also know that they increase the risk of yeast infection for both mom and baby. However, to my knowledge, no long-term studies have been done to follow the health impacts of IAP in children past the age of one. It has been noted that breastfeeding does have a positive recovery effect at reducing the ensuing dysbiosis.

It would be much less stressful to avoid having to make the decision of whether or not to have antibiotics during labour by testing GBS negative in the first place. In this area, we do see a ray of hope. There is some evidence to suggest that certain probiotic strains taken during pregnancy can reduce the risk of testing GBS positive, in women with no history of GBS as well as in those with previous GBS-positive tests (in previous or current pregnancy).

The trouble is a lack of consensus in which strains, doses, and applications are being studied, making reviews and global recommendations very difficult. Based on my own incomplete review, I would advise that Lactobacillus rhamnosus and Lactobacillus reuteri are the species coming out on top, although there is a very wide array of strains being studied with some impact dependent on dosage strength and length of treatment.  From what I have read thus far, I would NOT recommend Lactobacillus acidophilus as the primary therapeutic species in your intervention.

My Pregnancy Probiotic Recommendations

For my patients, I routinely recommend a probiotic with the two strains mentioned above prophylactically starting at the beginning of the third trimester and continuing on until birth. (UltraFlora Women’s from Metagenics is a good source.)  You want to make sure whatever supplement you choose has at least 1 billion CFU of each per dose. This appears to be the minimum effective dosage, with some studies going as high as 7.5 billion.

If a mom has additional risk factors for BV (bacterial vaginosis) or GBS (including UTI during pregnancy, antibiotic-usage during pregnancy, previous positive tests, or yeast imbalances), then I recommend a beneficial yeast probiotic containing Saccharomyces boulardii in addition to the bacterial microbiota support. (Usually with Sacro-B from Thorne Research.)  This strain is very effective at knocking down the "bad guys” and giving the “good guys” a preferential growth advantage.  Other dietary strategies (such as limiting sugar intake) and herbal antimicrobials also have a beneficial effect and may be paired with probiotics for the prudent or concerned mother.

There are several protocols out there that also include intra-vaginal treatment, whether of a probiotic supplement or other antimicrobial agents. I believe there is likely good effectiveness of this means of intervention, but it is outside my scope and comfort zone for me to recommend them directly. I would suggest Dr Aviva Romm as a good resource if this is something that you want to look into further for yourself.

Read this blog to learn more about Probiotics During Pregnancy.

*Note: Based on a reported recent increased the sensitivity of the testing being used and on more recent literary reflection, my current recommendations are under review.  Starting interventions earlier and using higher doses may be required for a more consistent protective effect.

In many government sources (and, based on patient reports, several MDs in Kelowna), they recommend automatically giving antibiotics if a mom was GBS positive in a previous pregnancy.  I do not like this approach. We know that within the same person GBS colonies vary considerably over time, which is why we test as close to birth as possible. Furthermore, there are already studies showing that within the same pregnancy, a positive GBS test can be remedied by birth.  Based on this, I recommend testing moms even if they were GBS positive in a previous pregnancy and making intervention decisions based on the more current information.  If possible, I would also encourage moms to advocate for GBS screening on the earlier side so that they have the potential opportunity for a second test if the first came back positive but baby stays put until 40 weeks. This would give them a chance to apply fervently the available natural remedies and hopefully reduce the risk of necessity for IAP.

On a more positive note, the impacts of maternal vaginal dysbiosis during pregnancy are becoming much more commonly examined by medical professionals.  At the well-respected BC Women's Hospital in Vancouver, it is becoming routine to test mothers with a history of preterm delivery for bacterial vaginosis, as this is recognized as a preventable cause of early membrane rupture and preterm delivery.  Knowledge is power!

As a heads-up, there are also GBS vaccines under development.  Although I appreciate the attempt to reduce the need for antibiotic exposure to mom and babe during labour, I'm a little weary, especially considering the safety of alternative approaches.  We shall see how this line of intervention develops in the next few years.

20 Week Infant Ultra Sound

To Recap & Reiterate

  • Group B Strep is common and considered normal vaginal bacteria in up to 25% of women.
  • Start taking a high dose probiotic containing Lactobacillus rhamnosus and Lactobacillus reuteri by the start of the first trimester.
  • Consume a nutrient-dense diet and eliminate sugar.
  • Know you have a choice in what happens to you and your baby during birth. Do your own research and stand for the decisions that feel right to you.
  • Breastfeed. Breastfeeding has the most noted and consistent impact in restoring infant microbes after antibiotic exposure.

Select References

  1. Açikgöz ZC, Gamberzade S, Göçer S, Ceylan P. Inhibitor effect of vaginal lactobacilli on group B streptococci. Mikrobiyol Bul. 2005;39(1):17-23.
  2. Aloisio I et al.  Influence of intrapartum antibiotic prophylaxis against group B Streptococcus on the early newborn gut composition and evaluation of the anti-Streptococcus activity of Bifidobacterium strains. Appl Microbiol Biotechnol. 2014;98(13):6051-60.
  3. Azad MB et al. Impact of maternal intrapartum antibiotics, method of birth and breastfeeding on gut microbiota during the first year of life: a prospective cohort study. BJOG. 2016 May;123(6):983-93.
  4. De Gregorio PR et al. Preventive effect of Lactobacillus reuteri CRL1324 on Group B Streptococcus vaginal colonization in an experimental mouse model. J Appl Microbiol. 2015 Apr;118(4):1034-47.
  5. Hanson L et al. Feasibility of oral prenatal probiotics against maternal group B Streptococcus vaginal and rectal colonization. J Obstet Gynecol Neonatal Nurs. 2014; 43(3):294-304.
  6. Ho M 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. 2016;55(4):515-8.
  7. Olsen P, Williamson M, Traynor V, Georgiou C. The impact of oral probiotics on vaginal Group B Streptococcal colonisation rates in pregnant women: A pilot randomised control study. Women Birth. 2018;31(1):31-37.
  8. Zárate G1, Nader-Macias ME. Influence of probiotic vaginal lactobacilli on in vitro adhesion of urogenital pathogens to vaginal epithelial cells. Lett Appl Microbiol. 2006 Aug;43(2):174-80.
  9. Clinical trial underway - Effects of Oral Probiotic Supplementation on Group B Strep (GBS) Rectovaginal Colonization in Pregnancy. Natali Aziz, Stanford University.
  10. https://www.cdc.gov/groupbstrep/about/newborns-pregnant.html
  11. https://evidencebasedbirth.com/groupbstrep/
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