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Abstract Background Fetal growth restriction (FGR) is typically characterised as the fetus’ inability to reach its inherent growth potential. A growing body of evidence points to the important role of the maternal gut microbiota in FGR development. However, comprehensive research on changes in maternal–fetal gut and intrauterine microbiota related to FGR is lacking. Methods In this case–control study, we sequenced bacterial 16S rRNA from 35 maternal faecal, 35 meconium, and 31 amniotic fluid samples collected from 19 pregnant women diagnosed with FGR and 16 healthy controls. We identified putative bacterial taxonomic and functional characteristics associated with FGR by comparing these to control samples. Results We identified 34 differential operational taxonomic units (OTUs) in amniotic fluid, seven differential OTUs in maternal faecal matter, and two differential OTUs in meconium. Compared to controls, FGR subjects exhibited enriched bacterial OTUs of the genus Bacteroides in the maternal gut. They also had depleted OTUs of the order Enterobacterales and genus Pseudomonas in the amniotic fluid and genus Stenotrophomonas in the fetal gut. These altered bacterial OTUs showed a significant correlation with neonatal weight and fetal ultrasonographic indexes. Additionally, we identified differential microbial functional pathways related to glycan and lipid metabolism in the maternal gut. We developed diagnostic biomarkers for FGR based on the maternal–fetal gut and amniotic fluid microbiota. Conclusions This study offers a comprehensive overview of the shifts in microbial composition and functional pathways in the maternal–fetal gut and amniotic fluid microbiota related to FGR, and present novel insights into the development and screening of FGR. However, the assessment of contamination’s impact on meconium and amniotic fluid remains inconclusive, necessitating further rigorous experimentation to address this scientific inquiry in future studies.

Problem: Prenatal exposure to intrauterine inflammation (IUI) is a crucial event in PTB pathophysiology. However, the relationship between microflora and PTB is not fully elucidated. Method of study: In this study, we established an intrauterine inflammation mouse model via LPS intrauterine injection. The saliva and amniotic fluid were collected for 16s RNA gene sequencing. The levels of TNF‐α and IL‐1β in mouse amniotic fluid were determined by ELISA assays. Results: Up to 60% of the operational taxonomic units (OTUs) in the saliva and amniotic fluid of PBS‐treated mice were overlapped. LPS treatment‐induced changes in the abundance of oral and amniotic fluid microorganisms. Both immune‐associated probiotics, salivarius and mastitidis, were still detected in saliva (at significantly increased levels) after LPS‐induced intrauterine inflammation and almost no probiotics of any type were detected in amniotic fluid, suggesting that the uterine cavity seems to be more susceptible to LPS compared to the oral cavity. Moreover, the abundance of pathogenic bacteria Escherichia coli was increased in both saliva and amniotic fluid after LPS treatment. The level of TNF‐α and IL‐1β in amniotic fluid is positively related to the amniotic fluid E. coli abundance. Conclusions: The microbial composition of saliva and amniotic fluid of pregnant mice was similar. LPS‐induced intrauterine inflammation decreased the consistency of microbial composition in mouse saliva and amniotic fluid, increased the abundance of E. coli in saliva and amniotic fluid, and decreased the abundance of immune‐associated probiotics, especially in amniotic fluid. [ABSTRACT FROM AUTHOR]

Aims: To compared the amniotic fluid and vaginal microbiota of pregnant women, who developed gestational diabetes mellitus to those who did not, and explored if any differences exist in the composition and functional genes of their amniotic fluid and vaginal microbiota. Methods: We compared the amniotic fluid and vaginal microbiota of five GDM patients and five non-GDM pregnant women in the third trimester of pregnancy by using metagenomics, and analyzed the characteristics, functions, and differences between two groups. Results: The analysis of the amniotic fluid showed significant differences in genus and species. In contrast, there was no significant difference in vaginal microbial community structure between two groups. The alpha diversity in the GDM group was higher than the control, but the difference was not statistically significant. There was a statistically significant difference in the species-level beta-diversity measured by Bray–Curtis distance of the amniotic fluid communities between two groups, while no significant differences were observed in the vaginal microbiota. Regarding the functions, we observed that the microbial communities of the amniotic fluid and vaginal secretions were involved in the regulation of a variety of host metabolic pathways, including carbohydrate metabolism, membrane transport, energy, amino acid metabolism, nucleotide metabolism, etc. No significant differences were observed between two groups, but different sites exist. Conclusion: The amniotic fluid of this study was discovered to have a heterogeneous, albeit small in number, community of microorganisms.Our research suggests that gestational diabetes has a very limited impact on the amniotic fluid and vaginal microbiome. The composition and the functions of the microbiota at different sites are different.