Impact of maternal diet on microbiota and health during pregnancy: a systematic review and correlational meta-analysis

Background: Pregnancy complications like gestational diabetes mellitus (GDM), hypertensive disorders of pregnancy, and obesity are rising. Emerging evidence suggests dietary strategies targeting maternal microbiota, such as increased fiber or polyphenols, may help manage these conditions. Objectives: This study aimed to 1) synthesize existing evidence on the relationship between maternal diet and the gut microbiota, with a focus on its potential link to gestational outcomes, and 2) provide insights based on the available literature to inform future pregnancy guidelines. Methods: This systematic review included observational and interventional studies on pregnant females assessing maternal diet and gut microbiota. Searches were conducted in PubMed and Web of Science up to July 2025. Risk of bias was assessed using appraisal tool for cross-sectional studies, Risk Of Bias In Nonrandomized Studies – of Interventions, and Risk Of Bias 2 tools. Narrative synthesis and a correlational meta-analysis stratified findings by trimester and obstetric condition. Results: Across 29 studies involving 3077 pregnant females, high-fiber and vegetarian diets were consistently associated with increased abundance of taxa such as Roseburia spp. and Bifidobacterium spp., alongside more favorable metabolic markers. In contrast, high-fat and Westernized diets were frequently linked to reduced microbial diversity and increased proinflammatory taxa including Collinsella and members of the Lachnospiraceae family. In GDM pregnancies, interventions like medical nutrition therapy were associated with favorable microbial profiles, whereas proinflammatory diets were associated with reduced diversity. Meta-analyses indicated that maternal health status significantly moderated associations between fat intake and Gram-negative bacteria [Likelihood Ratio Test (LRT) = 53.929, P = 0.020], and between protein intake and Gram-positive bacteria (LRT = 68.735, P = 0.009), suggesting differential microbial responses by metabolic risk profile. Conclusions: This systematic review found that specific dietary components, particularly fiber, omega-3 fatty acids, and micronutrients, were associated with differences in maternal gut microbiota, with potential relevance to metabolic outcomes such as GDM, obesity, and hypertensive disorders of pregnancy. Meta-analysis results indicate that maternal health status significantly moderated the associations between dietary fat and protein intake and microbial taxa, suggesting that precision nutrition interventions warrant evaluation in metabolically at-risk populations. This study was registered at PROSPERO as CRD420251085137.