PLPPR4 and hydrops fetalis: The θπ ratio (Fig. 5d and e), EHH values (Fig. 6a and b), and allele frequency (Fig. 6c and d) of selected gene regions between tropical HF populations and temperate zones exhibited reduced genetic diversity, increased haplotype homozygosity, and shifted alternative allele frequency in the selective sweeps for PLPPR4 and PITPNB.Functional enrichment analysis using GO was performed for all overlapping genes (Fig. 6e).