Vaginal metabolic profiles during pregnancy: Changes between first and second trimester.

Area of Science:

• Reproductive biology
• Microbiome research
• Metabolomics

Background:

• The vaginal microbiome is crucial for maternal and neonatal health during pregnancy.
• Vaginal microbial composition changes significantly throughout gestation, typically decreasing diversity and increasing Lactobacillus species.
• These microbial shifts correlate with alterations in vaginal metabolite profiles.

Purpose of the Study:

• To characterize vaginal metabolic profiles across different gestational ages.
• To correlate metabolic profiles with microscopic evaluation of vaginal bacterial composition.
• To understand the role of vaginal metabolites in pregnancy pathophysiology.

Main Methods:

• 67 pregnant Caucasian women were enrolled, providing vaginal swabs at 9-13 and 20-24 weeks of gestation.
• Vaginal microbiome composition was assessed using the Nugent score, categorizing women into 'H' (healthy), 'I' (intermediate), and 'BV' (bacterial vaginosis) groups.
• Metabolomic analysis of vaginal swab supernatants was performed using 1H-NMR spectroscopy.

Main Results:

• A shift towards a lactobacilli-dominated microbiota and a reduction in dysbiosis were observed from the first to the second trimester.
• Significant decreases in bacterial vaginosis-associated metabolites (acetate, propionate, tyramine, methylamine, putrescine) were noted over time.
• Increased concentrations of lactate and amino acids (tryptophan, threonine, isoleucine, leucine) were found, characteristic of healthy vaginal conditions.
• The vaginal metabolome became less diverse and more homogeneous; BV-associated metabolic profiles in the second trimester resembled those of healthy/intermediate groups.

Conclusions:

• Vaginal microbial shifts during pregnancy are strongly associated with profound changes in the vaginal metabolome.
• The progression of pregnancy leads to a reduction in BV-associated metabolites and an increase in beneficial metabolites.
• These findings highlight the dynamic interplay between the vaginal microbiome and metabolome, contributing to a healthier pregnancy environment.