What question did this study set out to answer?

The aim is to evaluate the effect of oral probiotics on GBS carriage in pregnant women.

February 2, 2026Journal of Clinical Medicine0 citationsOpen Access

The Effect of Oral Supplementation with a Multi-Strain Probiotic Preparation on Group B Streptococcus (GBS) Carriage in Pregnant Women—A Pilot Study

KZKatarzyna Zych-KrekoraPolish Mother’s Memorial Hospital Research Institute OSOskar Sylwestrzak MKMichał Krekora

Key Points

The aim is to evaluate the effect of oral probiotics on GBS carriage in pregnant women.
Prospective, single-centre, open-label pilot intervention study
Included 10 pregnant women with GBS-positive swabs
Participants received a multi-strain probiotic orally at 2 × 2 g/day from 15 to 34 weeks
Microbiological swabs were collected at three different gestational weeks
10 participants had a positive GBS result at baseline
50% were GBS-negative at mid-pregnancy (22-25 weeks)
90% were GBS-negative at late pregnancy (34-35 weeks)
Median time to first negative result was 8.6 weeks
No adverse events related to the probiotic were reported

Abstract

Background/Objectives: Maternal rectovaginal carriage of Group B Streptococcus (GBS, Streptococcus agalactiae) is a major risk factor for vertical transmission and early-onset neonatal infection. Intrapartum antibiotic prophylaxis reduces early-onset disease but does not address antenatal carriage and may affect the maternal–neonatal microbiota. Microbiota-directed interventions, including probiotics, are being explored as complementary strategies. Methods: This prospective, single-centre, open-label pilot intervention study included 10 pregnant women (18–40 years) with singleton pregnancies and a positive vaginal and/or rectal GBS swab, without pre-gestational or gestational diabetes and without antibiotic use in the 4 weeks before enrolment. Participants received OMNi-BiOTiC® FLORA plus (multi-strain lactic acid bacteria, including Lactobacillus crispatus) orally at 2 × 2 g/day from the 15th to the 34th gestational week. Microbiological swabs were obtained at qualification (12–15 weeks), mid-pregnancy (22–25 weeks), and late pregnancy (34–35 weeks). Outcomes were described descriptively. Results: Among 56 screened pregnant women, 10 were GBS-positive (17.9%) and enrolled. All participants were GBS-positive at baseline. At 22–25 weeks, 5/10 (50%) had a negative GBS result. At 34–35 weeks, 9/10 (90%) were GBS-negative, while 1/10 (10%) remained colonised. Time to first negative result ranged from 7.6 to 20.2 weeks from supplementation start (median 8.6 weeks). No recurrences (negative-to-positive transitions) were observed between the second and third sampling points. No adverse events related to supplementation were reported. In contrast, among the 46 women who were GBS-negative at screening and did not receive probiotic supplementation, 14 (30.4%) were found to be GBS-positive at routine screening performed at 35–37 weeks of gestation. Conclusions: In this pilot single-arm study, oral supplementation with a multi-strain probiotic preparation during pregnancy was associated with a time-dependent reduction in rectovaginal GBS carriage and was well tolerated. These preliminary findings support the feasibility of larger randomised controlled trials incorporating microbiome profiling and neonatal outcomes.

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