Increased vaginal <i>Gardnerella vaginalis</i> abundance and reduced D-galactose metabolism are associated with preterm birth in older mothers with columnar ectopy in South China

Advanced maternal age is associated with adverse pregnancy outcomes. However, the impact of changes in maternal physiology, biochemistry, vaginal microbiome, and its metabolites related to reproductive age on pregnancy outcomes is uncertain. Multi-omics were used to analyze vaginal samples collected from 195 pregnant women of different age groups to characterize the factors affecting the occurrence of adverse pregnancy outcomes in older mothers. Results showed that advanced maternal age is associated with a higher risk of premature birth. Furthermore, columnar ectopy may also contribute to premature birth. Moreover, older mothers with columnar ectopy exhibited vaginal microbiome dysbiosis, characterized by an increase in <i>Gardnerella vaginalis</i> and a reduction in <i>Lactobacillus crispatus</i>. Functional analysis of the microbiome revealed that disruptions in the vaginal microbiome might contribute to columnar ectopy by influencing carbohydrate metabolism in the host, such as galactose metabolism. Finally, galactose-degrading enzymes of <i>L. crispatus</i> were enriched in older mothers with non-columnar ectopies. In addition, <i>G. vaginalis</i> promoted the occurrence of columnar ectopy, whereas the dominance of galactosidase in <i>L. crispatus</i> was protective against columnar ectopy. Our findings demonstrate that <i>L. crispatus</i> is a target to prevent columnar ectopy or age-associated premature birth. <i>G. vaginalis</i> and galactose can be diagnostic markers for the occurrence of adverse pregnancy outcomes in older mothers.IMPORTANCEAdvanced maternal age poses a growing challenge to maternal health globally, yet the mechanisms linking age-related physiological changes to adverse pregnancy outcomes remain unclear. This study identifies vaginal microbiome dysbiosis, characterized by increased <i>Gardnerella vaginalis</i> and reduced <i>Lactobacillus crispatus</i>, as a critical mediator of age-associated preterm birth in mothers with columnar ectopy. By integrating multi-omics analyses, we reveal that disruptions in galactose metabolism driven by microbial shifts may contribute to columnar ectopy development. Notably, <i>L. crispatus</i> galactosidase activity emerges as a protective factor, while <i>G. vaginalis</i> and galactose accumulation serve as potential diagnostic markers. These findings provide actionable targets for microbiome-based interventions to mitigate age-related pregnancy complications, advancing personalized strategies for maternal care.