Human genital tracts microbiota: dysbiosis crucial for infertility Original paper

What was reviewed?

This review explored the relationship between genital tract microbiota dysbiosis and infertility in both men and women. It discussed how microbial imbalances in the vaginal, endometrial, seminal, and placental microbiomes can impair fertility, leading to complications such as bacterial vaginosis, poor sperm quality, and pregnancy-related issues like preterm birth. The review also examined how these microbiota imbalances affect reproductive health, suggesting that hormonal influences and microbial exchanges between partners play critical roles in fertility outcomes. The authors aimed to provide insights into how microbiome alterations can be used for better personalization of infertility treatments.

Who was reviewed?

The review primarily focused on studies involving both male and female infertility, including those with unexplained infertility and those undergoing assisted reproductive technologies (ART). It incorporated data on microbial composition from both sexes, specifically examining how dysbiosis in vaginal, endometrial, seminal, and placental microbiota can contribute to infertility and affect the success of treatments like in vitro fertilization (IVF). The review also addressed how microbial imbalances influence reproductive outcomes, drawing from clinical findings related to sperm quality, bacterial vaginosis, and pregnancy complications.

What were the most important findings?

The review highlighted the critical role of Lactobacillus species in maintaining a healthy vaginal microbiome. A dysbiotic vaginal microbiome, characterized by low Lactobacillus dominance and an overgrowth of pathogens such as Gardnerella, Prevotella, Mobiluncus, and Ureaplasma, was strongly associated with infertility, bacterial vaginosis, and adverse pregnancy outcomes. It was noted that female microbiota composition directly impacts pregnancy, with non-Lactobacillus-dominated environments leading to an increased risk of preterm birth and recurrent miscarriage. Similarly, seminal microbiota imbalances, including the overgrowth of bacteria such as Ureaplasma and Enterococcus, negatively influenced sperm quality, including motility and morphology, thereby affecting male fertility. The review also emphasized the concept of microbial trade-off between partners, where microbial dysbiosis in one partner could influence the reproductive microbiota of the other, further complicating fertility issues.

What are the greatest implications of this review?

The review’s findings suggest that clinicians should consider the role of genital tract microbiota when diagnosing and treating infertility. The identification of dysbiosis, particularly the loss of Lactobacillus dominance, can serve as a useful diagnostic marker for reproductive health. Interventions aimed at restoring a healthy microbiome, such as the use of probiotics or antimicrobial therapies, could improve fertility outcomes and reduce complications during pregnancy. Furthermore, the concept of microbial trade-off between partners indicates that both individuals in a couple should be assessed and treated for microbiome imbalances, enhancing the chances of successful conception. The review calls for further research into microbiome-based diagnostics and therapeutics to offer more personalized and effective treatments for infertility.