Another methylation site we found associated with an increased risk of HF is cg19869422, located in SMG6. Studies have shown that SMG6, as an important component of the NMD complex [57], facilitates the efficient degradation of mutant mRNA with premature stop codons through mechanisms such as endonucleolytic cleavage, preventing the accumulation of abnormal proteins [58, 59]. This evidence concerns the gene SMG6 and hydrops fetalis.