RBP4 and hydrops fetalis: Cadherin 5 (CDH5), KNG1, lumican (LUM), RBP4, SERPINC1, and SERPINF1 are involved in the apoptosis of endothelial cells and related processes, and this process was predicted to be inactivated in MCO compared to that in the 1st HF (activation z-score =  − 1.985).