USP9Y and hydrops fetalis: Using Enrichr through online enrichment analysis, it was identified that 7 highly expressed IDS in HF group (EIF1AY, RPS4Y1, USP9Y, KDM5D, DDX3Y, NPPA and HBB) were related to Erythrocytes take up oxygen and release carbon dioxide, Physiological factors, Erythrocytes take up carbon dioxide and release oxygen, O2/CO2 exchange in erythrocytes, HDMs demethylate histones, YAP1-and WWTR1 (TAZ)-stimulated gene expression; 7 highly expressed IDs in normal group (TSIX, LOC28556 and XIST) were related to Fatty acid metabolism (Fig. 6).