Targeted proteomics revealed characteristic signatures: iIUGR featured low complement (<i>C4A|C4B</i>) and IGF proteins (<i>IGFALS</i>, <i>IGFBP3</i>) versus GDM and iLGA (<i>p</i> < 0.001); GDM + IUGR showed elevated <i>PZP</i> and <i>CD5L</i> versus iIUGR (<i>p</i> < 0.05); GDM + LGA was marked by high <i>C4BPA</i> and low <i>RBP4</i>, <i>SERPINA7</i> versus iLGA (<i>p</i> < 0.05). The gene discussed is C4B; the disease is fetal growth restriction.