To address whether the alterations in the expression of ECM components at the critical phase of lung development at P1 are associated with an altered expression of the growth factor TGF-β1 in the neonatal lungs of IUGR rats, we measured the expression of the gene encoding TGF-β1 and the TGF-β responsive gene PAI-1. The gene discussed is TGFB1; the disease is fetal growth restriction.