Though this study was based on fetuses with Hb Bart’s disease, it may theoretically be a model for sonographic study of fetal anemia secondary to other causes such as Rh isoimmunization or pavovirus-B19, etc. However, effectiveness in detection of fetal anemia using C/B ratio needs to be elucidated by further studies. This evidence concerns the gene GSTM1 and anemia (phenotype).