Interaction Between First-Trimester Energy-Adjusted Dietary Inflammatory Index and Educational Level on the Risk of Anemia During the Second and Third Trimesters: A Prospective Cohort Study

<b>Objectives</b>: The aim of this cohort study was to assess the associations of first-trimester energy-adjusted Dietary Inflammatory Index (E-DII) and maternal educational level with anemia during the second and third trimesters, as well as their potential interactions. <b>Methods</b>: This study enrolled 562 eligible pregnant women. Multivariable modified Poisson regression with robust variance was used to assess the associations of first-trimester E-DII and maternal educational level with anemia during the second and third trimesters. Restricted cubic splines (RCS) explored nonlinear associations, while additive and multiplicative interaction models evaluated the interaction between first-trimester E-DII and maternal education. <b>Results</b>: The participants, with a mean age of 29.45 ± 4.28 years, had an anemia incidence of 14.59% during the second and third trimesters. In fully adjusted models, higher first-trimester E-DII (T3 vs. T1) significantly increased anemia risk (RR = 2.30, 95% CI: 1.36-3.90). Lower education (below bachelor's degree) independently elevated anemia risk (RR = 2.27, 95% CI: 1.52-3.39). RCS revealed no significant nonlinear relationship between the E-DII and anemia (<i>p</i> > 0.05). Although no significant multiplicative interaction was observed, a positive additive interaction was identified between first-trimester E-DII and educational level on the risk of anemia after adjustment for covariates, including age, ethnicity, pre-pregnancy BMI, employment, and baseline serum iron, among others. The measures of additive interaction were statistically significant: RERI = 4.64 (95% CI: 1.51-11.34), AP = 0.68 (95% CI: 0.26-0.86), and S = 4.91 (95% CI: 1.16-20.69) (all <i>p</i> < 0.05). <b>Conclusions</b>: First-trimester pro-inflammatory diets and lower educational attainment independently predicted anemia during the second and third trimesters and demonstrated a significant positive additive interaction. Combined nutritional and educational interventions integrated into prenatal care targeting pregnant women with limited education could effectively reduce anemia in pregnancy and improve perinatal outcomes.