Implications of the vaginal microbiome and potential restorative strategies on maternal health: a narrative review

Abstract

The vaginal microbiome undergoes dramatic shifts before and throughout pregnancy. Although the genetic and environmental factors that regulate the vaginal microbiome have yet to be fully elucidated, high-throughput sequencing has provided an unprecedented opportunity to interrogate the vaginal microbiome as a potential source of next-generation therapeutics. Accumulating data demonstrates that vaginal health during pregnancy includes commensal bacteria such as Lactobacillus that serve to reduce pH and prevent pathogenic invasion. Vaginal microbes have been studied as contributors to several conditions occurring before and during pregnancy, and an emerging topic in women’s health is finding ways to alter and restore the vaginal microbiome. Among these restorations, perhaps the most significant effect could be preterm labor (PTL) prevention. Since bacterial vaginosis (BV) is known to increase risk of PTL, and vaginal and oral probiotics are effective as supplemental treatments for BV prevention, a potential therapeutic benefit exists for pregnant women at risk of PTL. A new method of restoration, vaginal microbiome transplants (VMTs) involves transfer of one women’s cervicovaginal secretions to another. New studies investigating recurrent BV will determine if VMTs can safely establish a healthy Lactobacillus-dominant vaginal microbiome. In most cases, caution must be taken in attributing a disease state and vaginal dysbiosis with a causal relationship, since the underlying reason for dysbiosis is usually unknown. This review focuses on the impact of vaginal microflora on maternal outcomes before and during pregnancy, including PTL, gestational diabetes, preeclampsia, and infertility. It then reviews the clinical evidence focused on vaginal restoration strategies, including VMTs.

Contribution of Lactobacillus iners to Vaginal Health and Diseases: A Systematic Review

“…Previous studies have reported that up to 40% of patients who failed assisted reproduction by in vitro fertilization (IVF) had an abnormal reproductive tract microbiome (Fanchin et al, 1998;Moore et al, 2000;Koedooder et al, 2019). Vaginal dysbiosis, including an elevated pH value, increased flora diversity, BV, vulvovaginal candidiasis, and trichomonal vaginitis, are recognized as risk factors for infertility (Campisciano et al, 2017;Moumne et al, 2021). Campisciano et al reported that the abundance of L. iners was associated with an increased infertility rate (Campisciano et al, 2020).…”

Special series on the role of the microbiome in reproduction and fertility

“…The microbiome of the reproductive tracts in both males and females contribute to maintaining homeostasis and protecting against pathogens. In females, the vaginal microbiome helps regulate pH and prevent the overgrowth of potentially harmful microorganisms, which can affect fertility and increase the risk of adverse pregnancy outcomes ( Moumne et al 2021 ). In males, the prostate and seminal microbiomes are thought to influence sperm function and reproductive success ( Farahani et al 2021 ).…”

Vaginal Microbiome in Reproductive Medicine

“…Interestingly, both application routes seem to be efficacious [ 86 , 87 ]. Orally administered probiotics, also referred to as food-grade supplements consisting of live microorganisms, may provide additional beneficial effects to vaginal health via the so-called “gut–vagina axis” by balancing gut microbiota and inhibiting/preventing ascension of urogenital pathogens from the rectum to vaginal tract, as well as stimulating the gut and systemic immune system [ 88 , 89 ]. Several demonstrably effective probiotic oral supplements were developed in recent years; the majority of these were used for the treatment of gastrointestinal conditions [ 90 ].…”