KDR and pregnancy disorder: KDR, also known as vascular endothelial growth factor receptor 2 (VEGFR2), was demonstrated to be elevated in the placenta of pathological pregnancy diseases (early pregnancy loss, PE) in many studies (Kumazaki et al., 2002; Plaisier et al., 2009; Fang et al., 2013; Sundrani et al., 2013).