Maternal Dietary B-Complex Vitamin Pattern and Risk of Complex Congenital Heart Defects in a Mexican Population

Background/Objectives: Congenital heart defects (CHDs) are among the most common congenital anomalies worldwide, and maternal nutrition during early pregnancy may influence their development. Although previous studies have mainly evaluated individual B-complex vitamins, the contribution of their combined dietary intake to CHD risk remains poorly understood. This study investigated the association between maternal dietary B-complex vitamin intake and the risk of complex CHDs in a Mexican case–control study. Methods: Maternal dietary intake during pregnancy was assessed using a validated food frequency questionnaire, and nutrient intakes were energy-adjusted. Principal component analysis was used to construct a B-Complex Index based on the combined intake of vitamins B1, B2, B3, B6, and B12. Associations were evaluated using multivariable logistic regression adjusted for maternal age, total energy intake, multivitamin supplementation during pregnancy, and periconceptional folic acid supplementation. Results: Mothers of children with complex CHDs had significantly lower dietary intakes of B-complex vitamins than control mothers. The B-Complex Index was independently associated with lower odds of complex CHDs (adjusted OR = 0.707, 95% CI: 0.586–0.843; p = 0.0001). Conclusions: These findings suggest that evaluating the overall maternal dietary pattern of selected B-complex vitamins may provide complementary information regarding the nutritional environment relevant to early cardiac development. Prospective studies integrating dietary assessment, biomarkers, and genetic susceptibility are warranted to confirm these findings and further elucidate the underlying biological mechanisms.