Background Immunoglobulin A (IgA) plays an important role in maintaining a healthy intestinal microbiome, but little is known about the interaction between local immunoglobulins and the vaginal microbiome. We assessed immunoglobulins (unbound and bound to bacteria), their association with vaginal microbiota composition and the changes over time in 25 healthy women of reproductive age. Results In both Lactobacillus crispatus-dominated and non-L. crispatus-dominated microbiota, IgA and IgG (unbound and bound to bacteria) were higher during menses (T = 1) compared to day 7‑11 (T = 2) and day 17‑25 (T = 3) after menses onset. The majority of vaginal bacteria are coated with IgA and/or IgG. Women with L. crispatus-dominated microbiota have increased IgA coating of vaginal bacteria compared to women with other microbiota compositions, but contained less IgA per bacterium. Presence of a dominantly IgA-coated population at T = 2 and/or T = 3 was also strongly associated with L. crispatus-dominated microbiota. In women with non-L. crispatus-dominated microbiota, more bacteria were uncoated. Unbound IgA, unbound IgG, and bound IgG levels were not associated with microbiota composition. Conclusions In conclusion, L. crispatus-dominated vaginal microbiota have higher levels of bacterial IgA coating compared to non-L. crispatus-dominated vaginal microbiota. Similar to its regulating function in the intestinal tract, we hypothesize that IgA is involved in maintaining L. crispatus-dominated microbiota in the female genital tract. This may play a role in L. crispatus-associated health benefits.

During pregnancy, vaginal colonization by Candida spp is common. Some studies suggest an association between asymptomatic vaginal Candida colonization and adverse pregnancy outcomes, but the evidence is inconsistent. This review aimed to systematically review the association between asymptomatic vaginal colonization by Candida spp and adverse pregnancy outcomes, including preterm birth. DATA SOURCES: We searched Ovid MEDLINE, Ovid Embase, and the Cochrane Central Register of Controlled Trials from inception to May 6, 2020 for published studies on vaginal Candida/yeast and pregnancy outcomes. STUDY ELIGIBILITY CRITERIA: Cohort studies, case-control studies, and randomized controlled trials that included pregnant women who were tested for asymptomatic vaginal Candida colonization and reported on adverse pregnancy outcomes were eligible. STUDY APPRAISAL AND SYNTHESIS METHODS: Two reviewers independently selected and extracted the data. Critical appraisal was performed using the Newcastle-Ottawa Quality Assessment Scale for cohort and case-control studies and the revised Cochrane risk-of-bias tool for randomized controlled trials. RESULTS: We found no significant difference in preterm birth rate between Candidapositive and Candida-negative women (odds ratio, 1.10; 95% confidence interval, 0.99e1.22; I 2 , 0%) in 15 studies among 33,321 women for either spontaneous preterm birth only (odds ratio, 1.13, 95% confidence interval, 0.97e1.31; I 2 , 0%) or all preterm birth (odds ratio, 1.04; 95% confidence interval, 0.79e1.35; I 2 , 21%). Subgroup analyses for a treatment strategy including only studies reporting on spontaneous preterm birth did not reveal any statistically significant associations either, although the odds ratio was increased for the untreated Candida-positive women (odds ratio, 1.28; 95% confidence interval, 0.90e1.81; I 2 , 13%) in 3 studies among 5175 women. Asymptomatic vaginal Candida colonization was not associated with small for gestational age, perinatal mortality, or any other adverse pregnancy outcome. CONCLUSION: Asymptomatic vaginal Candida colonization is not associated with preterm birth and other adverse pregnancy outcomes. Previous studies reported that treatment of this microorganism reduces preterm birth rate. Our results suggest that this effect is unlikely to rely on treatment of vaginal Candida.