Also, various clinical studies have revealed the association between certain eNOS gene variants (for example G894T, 4b/a, c.894G > T (p.(Glu298Asp)), g.-786 T > C, g.2051G > A, and g.1861G > A) and low serum level of NO in preeclamptic patients [104, 105], while the presence of AGT 704C allele is associated with a reduced risk of developing preeclampsia [105]. This evidence concerns the gene NOS3 and preeclampsia.