Alterations in maternal–fetal gut and amniotic fluid microbiota associated with fetal growth restriction

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.