Oral Probiotic Supplementation in Pregnancy to Reduce Group B Streptococcus Colonization (OPSiP)

  • End date
    Dec 23, 2023
  • participants needed
  • sponsor
    University of British Columbia
Updated on 24 February 2022
Accepts healthy volunteers


This is a double-blind randomized placebo controlled trial that will investigate whether the use of three specific species of probiotics taken orally in pregnancy from 25 weeks gestation will reduce the incidence of Group B Streptococcus (GBS) colonization. Participants will take 2 capsules and 1 lozenge per day of either probiotic or placebo from 25 weeks gestation. The primary outcome will be the study-specific vaginal/rectal swab collected after 35 weeks gestation and before delivery. A reduction in women testing positive for GBS would lead to a decrease risk to infants of GBS infection and a reduction in the use of antibiotics leading to less maternal and neonatal antibiotic exposure.



Group B streptococcus (GBS) infection of the newborn is a leading cause of neonatal morbidity and mortality in North America. Up to 30% of pregnant women are colonized with GBS. Half of the babies born to colonized mothers will become colonized themselves, and of those, about 1-2% may develop early onset GBS infection (EOGBS), which is associated with significant mortality (between 5% and 20%) and morbidity (71% bacteremia, 11% meningitis, 19% pneumonia). The current recommendation is for routine administration of IPA to women who test positive for GBS at term. Although IPA therapy may reduce the incidence of neonatal GBS infection, it can increase the risk of other infections such as E. Coli, neonatal thrush, and ampicillin resistant Enterobacteriaceae.

There is also accumulating evidence linking antibiotics in pregnancy with childhood asthma, childhood obesity, and obesity in later life. IPA is also associated with antibiotic resistance, diarrhoea (including Clostridium difficile), and fungal infections. There is a growing worldwide interest in utilizing probiotics to enhance and manipulate the human microbiome in order to reduce a wide range of communicable and non-communicable diseases. Probiotics have been studied extensively in pregnant women and are considered safe and well tolerated when ingested or used vaginally.

Probiotics in pregnancy may reduce GBS colonization and the need for intrapartum antibiotic prophylaxis through a number of mechanisms. Some probiotics produce antibacterial substances and film-like barriers to pathogens. By adhering to vaginal epithelial cells, probiotics also displace pathogens such as GBS. S. salivarius K12 has been shown to inhibit several GBS strains, including disease-implicated isolates from newborns and colonizing isolates from the vaginal tract of pregnant women. In vivo and in vitro studies demonstrate its ability to adhere to the vaginal epithelium and directly impair the growth and adherence of GBS.

Several pilot randomized trials of L. reuteri and L. rhamnosus show promise in their their ability to reduce GBS colonization and have been shown to be safe. In vivo and in vitro studies of various lactobacillus strains, including rhamnosus and reuteri, have demonstrated an inhibitory effect on GBS.

Preliminary research to date suggests the administration of probiotic supplements to women in pregnancy may reduce the incidence of GBS colonization, thus reducing the need to administer intravenous prophylactic antibiotics (IPA) to women during labour. The specific species of probiotics chosen for this trial create a combination of inhibitory and antibacterial effects that may result in a greater reduction of GBS colonization than shown in previous trials.

The study:

The OPSiP study is a three-year, two-centre, double blind randomized placebo controlled trial. The aim of this study is to assess if a combined daily oral supplementation of Lactobacillus rhamnosus, Lactobacillus reuteri and Streptococcus salivarius beginning from 25 weeks gestation and continued until delivery will reduce vaginal/rectal group B streptococcus (GBS) colonization rates. Secondary aims include reduction of maternal and neonatal antibiotic exposure, and maternal vaginal and urinary tract infections.

450 healthy pregnant women receiving care from a regulated maternity care professional and registered at either St. Paul's or BC Women's Hospitals in Vancouver, British Columbia will be recruited. Women will be introduced to the study through posters and flyers and information from their maternity care provider. Women will be provided with verbal and written information on the study and provide written consent to participate before being entered into the study. Women will be entered into the study following initial screening to confirm their eligibility to participate in the study and then randomized to the intervention or control group.

Women randomized to the intervention group will receive a daily combination of one lozenge and two capsules of oral probiotic supplements comprised of three probiotic species; Lactobacillus rhamnosus and Lactobacillus reuteri (Urex Plus VCap-5) and Streptococcus salivarius K12 (Blis K12). The control arm will receive identical placebos administered using the same route and regimen as the active probiotic. Both groups will begin taking their daily study lozenges and capsules at 25 weeks gestation until delivery.

Five study-specific swabs will be collected, three vaginal/rectal and two oral swabs. The first vaginal/rectal swab and the first oral swab will be obtained at intake, after randomization and prior to the start of the intervention. The second vaginal/rectal swab will be obtained at mid-point, between 29-33 weeks gestational age. The third vaginal/rectal swab and second oral swab will be collected between 35 weeks and delivery.

The primary outcome will be vaginal/rectal GBS status, ascertained from the last study-specific vaginal/rectal swab. Statistical analysis will be on the basis of intention to treat. Treatment effect will be estimated using logistic regression. A two-tailed p-value <0.05 will be considered significant.

Secondary analysis will be performed on last observation moving forward, protocol-compliant groups and with adjustment for care-provider type and use of other dietary probiotic sources.

Condition Group B Streptococcus Carrier in Childbirth
Treatment Placebo, Probiotic supplementation
Clinical Study IdentifierNCT03407157
SponsorUniversity of British Columbia
Last Modified on24 February 2022


Yes No Not Sure

Inclusion Criteria

Pregnant with a singleton
Gestational age less than 25+0 weeks
Over the age of 18
Registered for delivery, at one of the participating centres
Under the care of a regulated maternity care provider (midwife, obstetrician (OB), or family physician)

Exclusion Criteria

Unable to provide consent
Fetus has known major anomalies
Significant immunosuppression
Type I or Type II diabetes (non-gestational)
Previous infant with GBS (these women will automatically be advised to be treated with IV antibiotic therapy)
GBS bacteriuria diagnosed in present pregnancy (reasoning as per above)
Plans to use oral or vaginal probiotic supplementation/therapy (capsules/tablets/lozenges/drinks) during their pregnancy (outside of natural food sources; yogurt, kimchi, kombucha etc)
Enrolled in another study that involves the administration of a drug/product
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