This review followed a pre-registered protocol (PROSPERO CRD42024535368) and PRISMA 2020 reporting guidance. The authors searched MEDLINE and Embase via the OVID platform and PubMed for articles published from January 1, 2014, to October 31, 2025. Search terms addressed Streptococcus agalactiae carriage in mothers and pregnancy across the Asia-Pacific region. The search was limited to English-language publications.
Inclusion criteria comprised observational and case studies reporting rectovaginal GBS colonization prevalence in pregnant or postpartum women from East Asia, South Asia, Southeast Asia, and Oceania. Eligible specimen sites included vaginal, rectal, or perianal samples. Studies were excluded if prevalence estimates derived from fewer than 50 women or if rates could not be ascertained from laboratory sample data. Modeling, ecological, qualitative studies, systematic reviews, opinion pieces, and animal studies were excluded.
Search results were managed in Covidence for screening. Two reviewers independently screened titles and abstracts: one author screened 100% (Z.Q.T.) and a second author screened a 10% random sample (L.A.H.D.); both authors independently completed 100% of full-text screening and resolved disagreements by consensus. Duplicate records were removed during Covidence processing.
Data extraction was performed by one reviewer using Covidence and Microsoft Excel. Extracted variables included country, study period, design, study population, gestational age at sampling, number of women tested, number of positive GBS detections, detection method (culture or molecular, with or without enrichment), sampling site, serotype distribution and serotyping methods, AMR rates, and AMR testing methodology.
Quality assessment used the Joanna Briggs Institute Critical Appraisal Tool for analytical cross-sectional studies. The tool addressed eight criteria; studies scoring 6–8 were considered low risk of bias, 3–5 moderate risk, and 0–2 high risk. Studies judged high risk (score <3) were excluded from the meta-analysis.
For quantitative synthesis the authors pooled prevalences using a random-effects inverse variance model weighted by sample size, reflecting the assumption that included studies represent a random sample of a broader set of studies. Analyses were conducted in Stata version 19.0.
The systematic search identified 1,623 studies, of which 98 met inclusion criteria and were included in the meta-analysis. Across those studies, 978,150 pregnant women were tested for rectovaginal colonization, and 172,973 women were reported as colonized with GBS.
The pooled estimated prevalence of maternal rectovaginal GBS colonization in the Asia-Pacific region was 18.0% (95% CI 12%–23%). Geographic representation varied: the authors note limited study data from Southeast Asia and the Pacific/Oceania subregions.
Serotype distribution was reported in 24 studies. Among the serotypes evaluated, serotype III was the most commonly reported, with study-level proportions ranging from 5.0% to 100.0%. The review reiterates previously documented regional variation in serotype frequency and highlights that serotypes Ia, III, and V have been commonly observed in maternal colonization and in invasive infant disease in other reviews.
Antimicrobial resistance data were available in 30 studies. Reported AMR proportions to β-lactams—the first-line agents for intrapartum prophylaxis such as penicillin or ampicillin—were low, in the range of 0%–2.0% in the included studies. The review notes that clindamycin or vancomycin are used for persons allergic to penicillin, and that concerns about AMR emergence exist because of frequent antimicrobial use, but the pooled data here indicated low β-lactam resistance.
Additional descriptive findings in the source include references to the global burden of neonatal invasive GBS disease (reported elsewhere) and the recognition that most cases and deaths occur in low- and middle-income countries where screening and intrapartum antibiotic prophylaxis (IAP) implementation is limited.
The review concludes that maternal rectovaginal colonization with Group B Streptococcus is common in the Asia-Pacific region, with a pooled prevalence estimate of 18.0%. The predominance of serotype III in the serotyped studies aligns with prior literature indicating serotypes Ia, III, and V often account for a large share of maternal colonization and invasive disease in infants, while noting regional variation.
Low observed resistance to β-lactams in the included studies supports current first-line treatment recommendations that use penicillin or ampicillin for GBS prophylaxis and infection treatment. The authors highlight, however, ongoing concerns about antimicrobial drug resistance in the context of high antimicrobial use and recommend continued monitoring.
Important gaps identified by the authors include sparse data from Southeast Asian countries and the Pacific/Oceania subregion. These gaps limit region-specific estimates and may affect the accuracy of extrapolations used for burden estimates and policy planning. The authors recommend continued surveillance of GBS prevalence, serotype distribution, and AMR, especially in underrepresented countries, to inform effective prevention (including screening and IAP) and treatment programs.
Limitations of the review noted in the source include restriction to English-language publications and the exclusion of small studies or those lacking laboratory-derived prevalence data. The authors also applied a bias assessment and excluded high-risk studies from the pooled meta-analysis. Details on heterogeneity metrics and subgroup analyses are provided in the original article figures, tables, and appendix.
Overall, the systematic review and meta-analysis synthesize recent Asia-Pacific data through October 2025, documenting an overall maternal rectovaginal GBS colonization prevalence of approximately 18%, a predominance of serotype III among studies reporting serotypes, and generally low reported β-lactam resistance in the sampled studies. The authors call for strengthened surveillance in Southeast Asia and Pacific regions to guide local public health measures and clinical management.