Several studies have reported elevated ET-1 levels in preeclampsia and some of them demonstrated a positive correlation between ET-1 and the severity of symptoms (Taylor et al., 1990; Mastrogiannis et al., 1991; Benigni et al., 1992; Granger et al., 2006; George and Granger, 2011, 2012; George et al., 2012). This evidence concerns the gene EDN1 and preeclampsia.