Association of Vegetables-Fruits Dietary Patterns with Gestational Diabetes Mellitus: Mediating Effects of Gut Microbiota

(1) Introduction: Previous studies have found that diet can change gut microbiota, thereby affecting metabolic health. However, research on gestational diabetes mellitus (GDM) is still limited. Our study aimed to explore the mediating role of gut microbiota in the relationship between dietary patterns and GDM. (2) Methods: In this case-control study, 107 women with GDM at 24–28 weeks of gestation and 78 healthy pregnant women were enrolled. A semi-quantitative food frequency questionnaire (FFQ) was used to assess dietary intake over the previous month. Mediation analysis was performed to explore the link between dietary patterns, gut microbiota, and GDM. (3) Results: Among the five dietary patterns extracted, the high group (factor scores ≥ −0.07) of the vegetables-fruits dietary pattern had a 67% lower risk of developing GDM compared to the low group (factor scores < −0.07) (OR: 0.33; 95% CI: 0.15–0.74). In addition, a significant alteration was observed in gut microbiota composition among GDM pregnant women. Mediation analysis showed that the Lachnospiraceae family, Blautia, and Ruminococcus genus partially mediated the effect of vegetables-fruits dietary pattern on GDM, explaining 45.81%, 44.33%, and 31.53% of the association, respectively. (4) Conclusions: Adherence to vegetables-fruits dietary patterns during pregnancy may reduce the risk of GDM by altering gut microbiota composition.