The consistent down-regulation of the heme oxygenase 1 gene (Hmox1) along with the upregulation of multiple serpin peptidase inhibitors (Serpin1f and Serpinb5 among others) is in agreement with previous reports on the role of these hypoxia-related genes on placental development, IUGR and preeclampsia in humans and animal models38,39. This evidence concerns the gene HMOX1 and preeclampsia.