PSG5 and fetal growth restriction: Therefore, we could conclude that in vascular IUGR, only a minimal set of genes was transcriptionnally maintained in the placental tissue in order to prevent spontaneous abortion, (i) transcripts from genes of the respiratory cascade, (ii) IGFII, one isoform of which is the essential growth factor in placenta [20], and (iii) three genes of the PSG cluster.