METTL14 and hydrops fetalis: Cardiac hypertrophy, both physiological and pathological, is the enlargement of the heart and CMs, due to the adaptation to cardiac stress.327 It is reported that in exercise-induced physiological cardiac hypertrophy, the total mRNA m6A levels in the heart are significantly reduced, possibly due to the METTL14 down-regulation.316 Pathological cardiac hypertrophy is a major contributor to HF with preserved ejection fraction (HFpEF) or reduced ejection fraction (HFrEF), occurring in various cardiac diseases.