Tolvaptan is a highly selective vasopressin V2 receptor antagonist with a convincing safety profile that has demonstrated beneficial effects in HF contributing to reduced volume overload, improved symptoms, increased urinary output, and corrected sodium levels without affecting renal function and serum electrolytes through its action on neurohormonal signaling in CRS [108, 155, 157]. Here, AVPR2 is linked to hydrops fetalis.