CYP2A6 and hydrops fetalis: In the HF groups, heart failure with reserved ejection fraction (HFrEF) demonstrates greater downregulation in CYP enzyme-related genes (CYP2A6, CYP2D6) and FZD4 receptor-related gene; LOX enzyme-related genes (ALOX12, ALOX15B) and cysLTR2 receptor-related genes (CYSLTR1, CYSLTR2); and COX genes, including COX receptor-related genes (PTGFR, PTGIR, PTGIS).