The association between the dietary inflammatory index during pregnancy and risk of gestational diabetes: a prospective cohort study and a meta-analysis.

Introduction: To examine the association between dietary inflammatory index (DII) and risk of gestational diabetes mellitus (GDM).

Methods: A prospective birth cohort study was conducted in Iran. During the first trimester of pregnancy, food intake was measured using a food frequency questionnaire. Each participant's DII score was calculated, and then, the Cox proportional hazard model was used to calculate the hazard ratio (HR) and 95% CI of GDM across the quartiles of DII. We systematically searched the literature to conduct a meta-analysis of observational studies (PROSPERO: CRD42022331703). To estimate the summary relative risk for the highest versus lowest category of DII, a random-effects meta-analysis was performed. The certainty of evidence was assessed using the GRADE approach.

Results: In the prospective cohort study (n = 635 pregnant mothers), the multivariable HRs of GDM for the third and fourth quartiles of DII were 2.98 (95%CI: 1.98, 6.46) and 2.72 (95%CI: 1.11, 6.63), respectively. Based on a meta-analysis of six prospective cohorts and a case-control study (1014 cases of GDM in 7027 pregnant mothers), being in the highest category of the DII was associated with a 27% higher risk of GDM (relative risk: 1.27, 95%CI: 1.01, 1.59; I² = 50%; low certainty of evidence). A dose-response meta-analysis suggested a positive monotonic association between DII and GDM risk.

Conclusions: Our prospective cohort demonstrated a positive correlation between GDM risk and the inflammatory potential of diet in the first trimester of pregnancy. The results need to be confirmed by larger cohort studies.

Clinical trial number: Not applicable.