In this sense, the aim of the present work was to study the gene and protein expression through RT–qPCR and immunohistochemistry, respectively, of oxidative stress markers (NOX-1, NOX-2, iNOS, eNOS and PARP) in the placental tissue of women who underwent a first episode of psychosis during pregnancy (FE-PW) in comparison to healthy pregnant women. The gene discussed is NOS3; the disease is psychotic disorder.