Prevalence and risk factors of group B Streptococcus colonisation in intrapartum women: a cross-sectional study

A cross-sectional study was conducted at a Thai university hospital between November 2016 and March 2017 to evaluate the prevalence and risk factors of group B Streptococcus (GBS) colonisation in pregnant women who were admitted to the labour room for delivery. Rectovaginal specimens were collected and processed for the identification of GBS. Univariate and multiple logistic regression analyses were conducted to evaluate factors associated with GBS colonisation. Statistical significance was set at p < .05. Fifty-seven of 505 pregnant women (11.3%, 95% confidence interval [CI] 9.0-15.0%) were found to have GBS colonisation. Teenage pregnancy (odds ratio [OR] 3.83, 95% CI 1.13-13.02, p < .05), multi-parity (OR 3.59, 95% CI 1.69-7.60, p < .01) and non-Buddhist religions (OR 1.87, 95% CI 1.01-3.48, p < .05) were significantly associated with GBS colonisation. Intrapartum risk factors were not associated with GBS colonisation. Impact statement What is already known on this subject? The prevalence of GBS colonisation in pregnant women varies by geographic areas and ethnicities, ranging from 2.3 to 32.9%. Risk factors for GBS colonisation have been studied but the results were inconsistent. What do the results of this study add? This study reports the prevalence of GBS colonisation in intrapartum women in Southern Thailand to be 11.3%. We also identified some independent risk factors for GBS colonisation which were teenage pregnancy, multi-parity and non-Buddhist religions. To our knowledge, the relationship between religious belief and identification of GBS has never been reported before. We also found that intrapartum risk factors that have been used as the indication for intrapartum antibiotics administration have no correlation with GBS colonisation. What are the implications of these findings for clinical practice and/or further research? This study adds to the literature the prevalence and risk factors of GBS colonisation in the setting of a developing country. It also shows that intrapartum risk identification alone is not an optimal strategy to reduce infection associated with GBS. Instead, prenatal GBS screening should be encouraged to identify women with GBS colonisation to reduce the risk of infection and unnecessary antibiotics exposure.