GBS colonization remains common across Asia-Pacific pregnancies, with surveillance gaps in Southeast Asia
Among pregnant women in the Asia-Pacific region, group B Streptococcus colonization is common enough to keep obstetric screening and neonatal prevention squarely in focus. A systematic review and meta-analysis spanning 2014 through 2025 pooled data from 98 studies and 978,150 pregnant women, yielding an overall estimated rectovaginal colonization prevalence of 18.0%.
That estimate matters because maternal colonization is the key gateway for early-onset neonatal invasive disease, typically transmitted during delivery. In practical terms, the burden identified across this region means that prenatal detection is not an abstract surveillance exercise; it is the first step in deciding who should receive intrapartum antibiotic prophylaxis and who may otherwise pass the organism to a newborn at the most vulnerable moment.
A large pooled prevalence, but a highly uneven regional picture
The analysis drew from 1,623 records identified in MEDLINE, Embase, and PubMed, but only 106 studies met eligibility criteria after screening, and 98 entered the quantitative synthesis. Eight studies were excluded from meta-analysis because of high risk of bias, leaving a final evidence base that still encompassed a very large number of pregnancies. The pooled prevalence estimate came with wide uncertainty, 95% CI 12%–23%, and the authors observed substantial interstudy heterogeneity.
The data did not distribute evenly across the region. Most studies came from East Asia, while Southeast Asia contributed only 11 studies and Oceania 10, all from Australia. That imbalance is clinically important because prevalence estimates become less dependable when entire subregions are sparsely sampled. In this review, the pooled prevalence reached 21.0% in Oceania, 17.0% in East Asia, 14.0% in Southeast Asia, and 13.0% in South Asia, but the confidence around those figures depends heavily on how much data each subregion contributed.
Country income level also tracked with different pooled estimates. Pregnant women in high-income countries had a pooled prevalence of 20.0%, compared with 11.0% in upper-middle-income countries and 12.0% in low-middle-income countries. Those differences may reflect genuine epidemiologic variation, but they may also reflect differences in screening intensity, laboratory methods, sample sites, and access to antenatal care. In other words, what looks like geography can sometimes be a mixture of biology and detection infrastructure.
Screening methods shape what gets found
Most included studies sampled the vagina and rectum, which is the most informative approach for maternal rectovaginal carriage. Other studies used vaginal sampling alone, a smaller number used vaginal and cervical sampling, and several did not clearly specify the site. Such methodological variation can shift prevalence upward or downward, because rectovaginal carriage is not always captured by a single-site swab.
This is not a trivial technical detail. GBS colonization is a surface carriage state, so test performance depends on where the sample is taken and whether the laboratory method is culture-based or molecular. Enrichment, specimen source, and timing in gestation all influence detection. When surveillance programs compare prevalence across countries without standardizing those variables, they risk measuring the screening system as much as they measure the organism.
Across the broader evidence base, 29 studies derived from routine antenatal screening programs, most of them in Australia, Japan, Hong Kong, and Taiwan. That concentration suggests that the best-characterized part of the region is also the part with stronger prenatal screening systems. The absence of similar routine data from many Pacific and Southeast Asian settings leaves an important blind spot precisely where surveillance could most inform maternal and newborn prevention strategies.
Serotype III led, but serotype reporting was limited
Serotype data were available in only 24 studies, limiting firm regional conclusions. Even so, serotype III emerged as the most common type, with reported ranges from 5.0% to 100.0% across studies. That wide range is a reminder that serotype distribution can vary dramatically by country and by sampling frame, and it also reflects how sparse the serotyping literature remains compared with prevalence studies.
The serotype pattern matters because vaccine development and future immunologic prevention strategies depend on knowing which capsular types circulate most often in pregnant women and in disease-causing isolates. Serotype III has long been associated with invasive neonatal disease in many settings, so its prominence in maternal carriage remains epidemiologically relevant. If future maternal vaccines are to reduce early-onset infant disease effectively, they will need to match the serotype ecology of the populations most affected.
Beta-lactam resistance stayed low, but antimicrobial stewardship still matters
Thirty studies reported antimicrobial resistance rates, and β-lactam resistance remained low, at 0%–2.0%. That finding is reassuring because penicillin and ampicillin remain first-line options for GBS infection and intrapartum prophylaxis, while clindamycin or vancomycin are used for patients with penicillin allergy.
Resistance patterns, however, should not be interpreted as static. The widespread use of intrapartum antibiotics in high-income settings and broader antimicrobial exposure in many health systems can exert selective pressure over time. The review’s resistance data suggest that β-lactams remain a strong foundation for current prevention strategies, but continued monitoring is essential if treatment programs are to preserve their utility and avoid drifting into empiric practice that outpaces microbiology.
Public health implications center on regions with thin surveillance
The study makes one message plain: GBS colonization is common among pregnant women throughout the Asia-Pacific region, but the evidence base is still uneven, and the sparsest data come from Pacific and Southeast Asian countries. That gap is not academic. Without local colonization estimates, health ministries cannot easily calibrate screening policy, anticipate neonatal risk, or decide where intrapartum prophylaxis would have the greatest impact.
For clinicians, the findings support continued attention to maternal GBS status in antenatal care, especially where screening programs already exist. For health systems without routine screening, the review strengthens the case for building baseline surveillance first, because policy without local prevalence data is guesswork. The same is true for serotype monitoring: without knowing which strains dominate, prevention programs cannot judge whether future vaccines or updated protocols would fit the regional burden.
The review also exposes a familiar problem in infectious-disease epidemiology: the places with the least data may be the places where the consequences of undetected maternal colonization are hardest to absorb. That is why the authors’ call for continued surveillance in Pacific and Southeast Asian countries is not merely descriptive. It points to the operational step that must come before any durable prevention strategy—consistent, standardized, region-specific measurement of carriage, serotype, and antimicrobial susceptibility.