GSTM1 and hydrops fetalis: While the high prevalence of anemia, determined from Hb concentration cutoff values, is well established in HF populations (Brucks et al. 2004; Klapholz et al. 2004; Berry et al. 2005), the cause of anemia is commonly attributed to hemodilution owing to presumed PV expansion (Senni et al. 2014).