Measurements made in the umbilical cord after puncture fetal blood showed that compared to normal fetuses, fetuses with IUGR are often hypoxic, hypercapnic and acidotic. Pathological placental and fetal oxygenation is considered as a main element of IUGR. To this day, there is no non-invasive exploration method of this oxygenation. The only ways to monitor IUGR are "indirect" ultrasonic analysis of fetal growth and uteroplacental Doppler spectra. Functional BOLD (Blood Oxygen Level dependent) MRI, already used to investigate cerebral, tumor, cardiac oxygenation, highlights local variations of oxygenation. The purpose of this study is to obtain non invasive data of fetoplacental oxygenation through functional BOLD MRI. Comparing data on eutrophic fetuses and IUGR fetuses will determine the potential contribution of this technique in the diagnosis, treatment and medical management of dysfunctional placentas associated with an increased risk of IUGR.