BMI1 and hydrops fetalis: Another group of genes exerting higher expression in the mammary tissue of HF than LM comprised factors essential for the maintenance of hematopoietic stem cells’ pools, and for mammary gland involution after lactation (LIF), as well as maintenance of cellular homeostasis, mammary epithelium growth, and stem cells activity (BMI1) (Pietersen et al. 2008; Mathieu et al. 2012).