NPPB and hydrops fetalis: These studies focused on the presence of diastolic HS such as S3 or S4; however, S3 or S4 was not evident in the present participants; they were all ambulatory and did not exhibit overt HF upon visiting our outpatient clinic, and 13 of them (32.5%) had HF defined by NT-proBNP level ≥ 300 pg/ml.