Our data, together with evidence that secretion of soluble HLA-G by in vitro fertilized human embryos is associated with a higher pregnancy rate [63,64] and that reduced levels of soluble HLA-G during early pregnancy correlate with a higher incidence of preeclampsia [65], suggest that KIR2DL4 has a positive role in reproductive success. This evidence concerns the gene HLA-G and preeclampsia.