In HF samples, four m5C regulators (NSUN6, DNMT3A, DNMT3B and ALYREF) were greatly upregulated, while five (NOP2, NSUN3, NSUN7, DNMT1 and TRDMT1) were downregulated compared to NFDs in the training set. The gene discussed is ALYREF; the disease is hydrops fetalis.