Although prior studies using subjects with European ancestry have identified associations between candidate SNPs in the introns of PITX2, ABO, ACTN2, MYOZ1, SYNPO2L, BAG3, and CDKN1A [23,33], such an analysis of a combined database constructed from a number of different cohorts results in an increase in the heterogeneity of the etiology and clinical manifestation of HF; this then leads to a reduction in the statistical power [33]. The gene discussed is ABO; the disease is hydrops fetalis.