Vaginal progesterone is associated with decreased group B streptococcus colonisation at term: a retrospective cohort study.

Objective: To investigate whether women using intravaginal progesterone suppositories for preterm birth prevention during pregnancy will have lower rates of group B streptococcus (GBS) colonisation at term, compared with women receiving intramuscular 17-alpha-hydroxyprogesterone caproate.
Design: This was a retrospective observational cohort study of women who were prescribed a progestogen during their pregnancy for preterm birth prevention, and who delivered at term.
Setting: A tertiary referral hospital in central Ohio.
Population: Patients who were prescribed a progestogen during their pregnancy for preterm birth prevention between 2004 and 2017 were included in the study. Patients who delivered at <37 weeks of pregnancy, switched progestogen type during the pregnancy, or had a pessary or cerclage placed were excluded.
Methods: Baseline characteristics were compared using Mann-Whitney U-test or Chi-square test as appropriate. The association between type of progestogen and GBS colonisation was assessed using bivariate and multivariable analyses.
Main Outcome Measures: The primary outcome was GBS colonisation.
Results: In all, 565 patients were included in the study, of whom 173 received intravaginal progesterone, and 392 17-alpha-hydroxyprogesterone caproate. Patients receiving intravaginal progesterone were less likely to be colonised with GBS (19.7 versus 28.1%). After adjustments for potential confounders were made in a multivariable logistic regression analysis, receiving intravaginal progesterone suppositories (adjusted odds ratio [OR] 0.61, 95% CI 0.39-0.95) was associated with reduced GBS colonisation.
Conclusions: Intravaginal progesterone is associated with a decreased prevalence of rectovaginal GBS colonisation at term.
Tweetable Abstract: Vaginal progesterone is associated with a lower incidence of rectovaginal GBS colonisation, compared with 17α-hydroxyprogesterone caproate.
(© 2019 Royal College of Obstetricians and Gynaecologists.)