An analysis of the Vaginal microbiome and the impact of infections on female infertility, Cervical Intraepithelial Neoplasia (CIN), and Cervical cancer

Abstract

For healthy reproduction and appropriate vaginal function, keeping the vaginal microbiota in balance is crucial.  Both pathogenic and nonpathogenic microbes are present inside the vagina, among them Lactobacillus is the most predominant. Lactobacillus gives protection against a wide range of pathogenic infections by producing lactic acid, hydrogen peroxide, and bacteriocins. A low amount of Lactobacillus strains and a higher amount of facultative anaerobic pathogens inside the vagina consequently lead to vaginal microbiota dysbalance. Female vaginas with a lower concentration of vaginal Lactobacillus are more prone to get upper genital tract infections, sexually transmitted infections, and other anaerobic pathogenic infections. Dysbiosis of the vaginal microbiota is strongly associated with infertility, poor pregnancy rate, pregnancy complications, spontaneous abortion, preterm birth, and frequent abortion. Female infertility is one of the most complex reproductive diseases and there is no effective way to get out of this problem to date. Several infection conditions like bacterial vaginosis, pelvic inflammatory diseases, and endometritis are related to adverse reproductive outcomes and infertility via disturbing normal immunity, normal vaginal microbial composition, regulating pathophysiological pathways, and inducing inflammation. Pathogenic bacteria including Neisseria gonorrhoeae, Chlamydia trachomatis, Trichomonas vaginalis, herpes simplex, Mycoplasma genitalium are mainly responsible for infertile conditions.  The aim of this review is to show the link between vaginal microbial disbalance and female infertility. This review also summarizes the effects of various inflammatory conditions, and infectious diseases of the reproductive system on female infertility. Several pathogenic microbes including sexually transmitted microorganisms and their impacts on female infertility are also reviewed in this paper.