GSTM1 and hydrops fetalis: Figure 1 demonstrates the distribution of the Hb/RDW ratio in the HF cohort. The mean Hb/RDW ratio was 0.85 ± 0.18; and median was 0.85 (interquartile range 0.72–0.98). We divided the cohort into six quantiles based on the Hb/RDW ratio <0.25, 0.25–0.49, 0.5–0.74, 0.75–0.99, 1–1.24, >1.25. The characteristics of the patients stratified according to the Hb/RDW ratio quantiles are presented in Table 1.