Diferenças Na Microbiota Vaginal Entre Mulheres Férteis E Inférteis: Uma Revisão Sistemática Com Meta-Análise

Abstract

Infertility is a public health issue that affects a significant portion of the global population, compromising reproductive capacity and causing social and emotional impacts. Various factors may be associated with this condition; however, a considerable proportion of cases still lack an apparent etiology and are classified as idiopathic. Given the growing interest in the role of vaginal microbiota in reproductive outcomes, this systematic review with meta-analysis aimed to evaluate, based on the available studies, whether there are significant differences in the composition of the vaginal microbiota between fertile and infertile women. It was hypothesized that fertile women would present a greater abundance of Lactobacillus spp., while infertile women

would exhibit a higher presence of bacterial genera associated with dysbiosis. Case- control studies involving fertile and infertile women, published in English over the past

fifteen years, were included. The review protocol was previously registered on the PROSPERO platform (registration number: CRD420251059918). Searches were conducted in the PubMed and Embase databases using descriptors based on the PICO strategy. Data extraction was performed independently by two researchers. Heterogeneity was assessed using Cochran’s Q test and the I2 statistic. The quantitative synthesis was carried out using RevMan 5.3 software, applying fixed- or random-effects models. Ten studies were included in the systematic review, totaling 992 participants, with five studies used in the meta-analysis. The pooled analysis revealed a higher bacterial abundance in the fertile group (MD = 4.64; 95% CI: 0.55– 8.74; p = 0.03; I2 = 98%). Stratification by bacterial genera showed higher levels of Lactobacillus spp. (p = 0.27), Gardnerella spp. (p = 0.02), and Prevotella spp. (p = 0.03) in the fertile group, with statistical significance for the latter two. Despite the lack of significance for the Lactobacillus genus, individual statistical analysis indicated significantly lower levels of three Lactobacillus species in infertile women (p < 0.00001). The risk of bias assessment, conducted using the ROBINS-I tool, indicated a serious risk in most studies, mainly due to the lack of control for confounding factors. The quality of the evidence, evaluated using the GRADE system, was considered very low to moderate. Thus, despite the confirmation of the association between Lactobacillus and fertility, the unexpected findings of Gardnerella spp. and Prevotella spp. in the fertile group, contrary to the existing literature, may be related to methodological inconsistencies, reinforcing the need for more homogeneous and robust studies.