Intra uterine growth retardation is a major cause of perinatal morbidity and mortality. These are due to prolonged intra uterine hypoxia and complications from subsequent induced prematurity. Fetal arterial doppler measurements, and more recently venous Doppler measurements, help choosing the ideal moment for delivering these fragile fetuses. Nevertheless, venous doppler measurements should be combined to other monitoring tools, used longitudinally and only when very preterm birth is expected.