Association Between Maternal Dietary Isoflavone Intake During Pregnancy and Childhood Allergic Rhinoconjunctivitis: The Japan Environment and Children’s Study

<b>Background/Objectives:</b> Isoflavone (ISO) may have immunosuppressive and promoting effects. In this study, we aimed to examine the association between maternal dietary ISO intake during pregnancy and childhood allergic rhinoconjunctivitis at the age of 3 years using the Japanese Birth Cohort data. <b>Methods</b>: Overall, 78,549 mother-child pairs were studied. Maternal dietary ISO intake (the sum of genistein and daidzein) during pregnancy was evaluated using a food frequency questionnaire. Information on physician-diagnosed allergic rhinoconjunctivitis was collected from the caregiver-reported questionnaire. After classifying ISO intake into quartiles (Q1: reference), multivariable logistic regression analysis was employed to explore the association with allergic rhinoconjunctivitis. <b>Results</b>: No association was observed between maternal ISO intake and allergic rhinoconjunctivitis in any child. However, in the sex-stratified analysis, maternal ISO intake linked to allergic rhinoconjunctivitis in female children positively (Q2, adjusted odds ratio [aOR]: 1.22, 95% confidence interval [CI]: 1.06-1.40; Q3, aOR: 1.17, 95% CI: 1.01-1.35; Q4, aOR: 1.24, 95% CI: 1.07-1.44). <b>Conclusions</b>: Maternal dietary ISO intake during pregnancy was sex-specifically linked to childhood allergic rhinoconjunctivitis in children. These findings provide insights into the need for estimating the optimal ISO consumption during pregnancy for allergy avoidance in children.