REN and hydrops fetalis: Since their first publication, the European Society of Cardiology (ESC) guidelines have always recommended the use of renin-angiotensin (RAS) inhibitors and beta-blockers (BBs) for all patients with HF with reduced ejection fraction (HFrEF) and New York Heart Association (NYHA) class II–IV disease, as these drugs are known to reduce mortality and morbidity [1, 14–19].