The vaginal microbiota and preterm birth: A systematic review

Area of Science:

• Obstetrics and Gynecology
• Microbiology
• Reproductive Health

Background:

• The vaginal microbiota, a complex ecosystem of microorganisms, plays a crucial role in maintaining reproductive health.
• Alterations in the vaginal microbiome composition are implicated in various obstetric complications, including preterm birth.
• Bacterial vaginosis, characterized by a reduction in Lactobacilli, is a known risk factor for preterm delivery.

Purpose of the Study:

• To systematically review and investigate the association between vaginal microbiota composition during pregnancy and the risk of preterm birth.
• To identify specific microbial species and community structures linked to adverse pregnancy outcomes.
• To explore potential biomarkers and influencing factors related to preterm birth and vaginal dysbiosis.

Main Methods:

• A systematic literature search was conducted across Scopus, Web of Science, and PubMed for studies published between January 2014 and June 2024.
• A total of 2194 articles were screened, with 14 full-research articles ultimately included in the review.
• Data extraction focused on vaginal microbiota composition, demographic factors, and preterm birth incidence.

Main Results:

• Demographic factors like ethnicity, age, substance use, and gestational age were found to influence vaginal microbiota composition.
• A decrease in Lactobacillus crispatus, Lactobacillus gasseri, and Lactobacillus jensenii, alongside a relative increase in Lactobacillus iners, was associated with an elevated risk of preterm birth.
• Increased prevalence of Ureaplasma, Mycoplasma, and Gardnerella species, as well as altered cytokine profiles (increased IL-1β, IL-6, MIP-1β; decreased β-defensin-2), were linked to higher preterm birth rates.

Conclusions:

• Specific alterations in the vaginal microbiota during pregnancy are significantly associated with an increased risk of preterm birth.
• The identified microbial signatures and inflammatory markers provide potential targets for risk assessment and intervention.
• Further research is warranted to establish causal relationships and develop effective strategies to mitigate preterm birth associated with vaginal dysbiosis.