Abstract
BACKGROUND: Gestational diabetes mellitus (GDM) affects 7-14% of pregnancies, increasing maternal and neonatal complications. Phytochemical-rich diets, abundant in plant-based foods, may improve glucose metabolism and reduce inflammation. The phytochemical dietary index (PDI) measures intake of such foods, but prospective data on GDM risk are scarce. This study aimed to examine early-pregnancy PDI in relation to subsequent GDM risk in a large birth cohort. METHODS: A total of 2,770 pregnant women (mean age 29.61 ± 4.55 years; mean pre-pregnancy BMI 23.96 ± 1.19 kg/m2) from the Women's Health Center of Shanxi were included. Dietary intake was assessed using a validated food frequency questionnaire. The plant-based diet index (PDI) was calculated as the proportion of daily energy intake from whole grains, fruits, vegetables, legumes, nuts, seeds, and olive oil. Participants were divided into PDI quartiles. GDM was diagnosed at 24-28 weeks' gestation using a 75 g oral glucose tolerance test based on IADPSG criteria. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs), adjusted for confounders. RESULTS: GDM occurred in 377 women (13.6%). Higher PDI was inversely associated with GDM risk (P-trend <0.001). Each 10% increase in PDI was associated with a 14% lower odds of GDM (OR 0.86; 95% CI: 0.82-0.91). Higher PDI was associated with lower risk of neonatal hypoglycemia (OR 0.93; 95% CI: 0.92-0.95) and better maternal biochemical profiles, including lower fasting glucose, HbA1c, post-load glucose, triglycerides, total cholesterol, and higher HDL cholesterol. CONCLUSIONS: Higher early-pregnancy PDI was associated with substantially lower risk of GDM, reduced neonatal hypoglycemia, and improved maternal metabolic profiles. Our findings support the integration of phytochemical-rich dietary guidance into early prenatal care.