Dietary fiber supplementation mitigates gestational diabetes risk and preterm birth via gut microbiota modulation: a randomized controlled trial

Background Gestational Diabetes Mellitus (GDM) poses severe health risks to mother and child, yet effective, non-invasive preventive strategies remain elusive. While the gut microbiota is known to influence glucose metabolism, its potential as a therapeutic target and predictive biomarker in high-risk pregnancies is underexplored. This study investigated whether soluble dietary fiber supplementation could remodel the gut microbiome to prevent GDM and improve pregnancy outcomes. Methods We performed a single-center, randomized controlled trial with 98 pregnant women at elevated risk for GDM. For 5 weeks, from 20 to 24 +6 weeks of pregnancy, participants were randomly assigned to either a fiber group (getting soluble fiber supplements every day) or a control group (getting normal care). Clinical outcomes encompassed OGTT results, gestational weight gain (GWG), and delivery outcomes. We used 16S rRNA sequencing to look at changes in gut flora. Furthermore, we developed a novel nomogram integrating clinical variables with microbial signatures to predict GDM risk. Results Although GDM incidence did not statistically differ, the fiber group exhibited significantly improved glycemic excursions (predominantly lower 1h-PG, and reduced whole-OGTT glucose AUC and iAUC), reduced GWG during the 5-week intervention period (1.83 vs. 2.54 kg; P = 0.016), and a complete absence of preterm births (0% vs. 12.0%; P = 0.040). Microbiome analysis revealed that fiber intake enriched Bifidobacterium and Limosilactobacillus while suppressing Phascolarctobacterium . Functional prediction indicated a downregulation of inflammation-related pathways (HIF-1, AMPK) in the Fiber group. Crucially, a prediction model combining clinical factors with a specific “micro-balance” ( Bifidobacterium ratio) achieved superior predictive accuracy (AUC 0.821) compared to clinical factors alone. Conclusions Preliminary findings suggest that dietary fiber supplementation serves as a potent “biotic” intervention in high-risk pregnancies, improving 1-hour postprandial glucose homeostasis and eliminating preterm birth in this cohort. The mechanism appears associated with the specific enrichment of Bifidobacterium . Additionally, we validated a novel clinical-microbial nomogram, suggesting that integrating gut microbiome data can significantly enhance GDM risk stratification. Future extensive research is need to confirm these results.