Dlk1 is expressed in the endothelial cells of the placental labyrinth 21, the interface between the maternal and foetal circulations that allows nutrient exchange with the foetal vasculature 42, prompting us to determine whether the altered function of these endothelial cells in Dlk1-null animals may be resonsible for the IUGR. The gene discussed is DLK1; the disease is fetal growth restriction.