NPPB and hydrops fetalis: BMSC‐derived exosomes were capable of enhancing the expression level of KLF4 in cardiomyocytes, decreasing the expression levels of myocardial damage markers BNP and hs‐TnI, as well as inflammatory factors TNF‐α, IL‐6, IL‐1β, sST2, and Gal‐3, thereby alleviating HF injury.