Maternal macronutrient intake and gestational diabetes: systematic review of prospective observational studies and dose-response meta-analyses

Background Gestational diabetes mellitus (GDM) is a common pregnancy complication associated with markedly elevated risk of type-2 diabetes in later life. Pregnancy or pre-pregnancy diet is a likely risk factor for GDM, with macronutrients—including proteins, fats, carbohydrates, and alcohol—being the primary dietary components to influence risk. In this study, we have conducted a systematic review and meta-analyses of pregnancy or pre-pregnancy dietary macronutrient intakes, including by source and type, on GDM occurrence to better elucidate the role of maternal diet on GDM. Methods We ran an online search on 15 August 2025 in OVID Medline, EMBASE, and EBM Reviews, augmented with reference searching to identify prospective observational studies reporting pregnancy or pre-pregnancy dietary intakes and GDM incidence. Screening, data extraction, and risk of bias assessment using the Newcastle–Ottawa Scale were performed by at least two reviewers. Macronutrient exposures and GDM incidence were considered with random effects higher versus lower (HvL) and dose-response analyses. Certainty of evidence was then considered with GRADE to comment on maternal macronutrient intakes and GDM. Results From 3990 initial titles, we identified 25 prospective observational studies of 115,496 pregnant women reporting at least one macronutrient intake and GDM. There was moderate certainty evidence that animal-sourced protein (HvL: RR 1.62 (95% CI 1.20 to 2.18) I2 82%) and animal-sourced fat (HvL: RR 1.59 (95% CI 1.34 to 1.88) I2 0%) intakes were associated with higher GDM in a dose-response manner. Total protein (HvL: RR 1.63 (95% CI 1.22 to 2.18) I2 64%) and vegetable fat (HvL: RR 1.25 (95% CI 1.06 to 1.47) I2 0%) showed positive associations with outcome in HvL but without dose response, while dietary fiber (HvL: RR 0.65 (95% CI 0.44 to 0.96) I2 89%) was the only macronutrient to indicate a protective effect against GDM with higher intakes in a dose-response manner, with moderate certainty evidence. Conclusions This study is the first to consider maternal intake of all macronutrients, including by source and type, on GDM occurrence. Our findings are largely in line with healthy dietary advice for the general population (promoting high fiber and low animal-sourced fat intakes); however, higher protein intakes (both total and animal-sourced) may be a specific concern that is not currently considered in dietary guidance during pregnancy, requiring further research. Trial registration PROSPERO (CRD420251001515).