The purpose of this study is to evaluate the use of functional MRI in pregnant women as a non-invasive diagnostic tool to detect placental insufficiency and differentiate healthy fetuses from the intra-uterine growth restricted ones. Functional MRI in pregnant women can detect a variation of the MRI signal (called BOLD effect) from the placenta and the fetus when the mother is breathing pure oxygen. This study aims hence to demonstrate the difference in the BOLD effect between normal feto-placental units and growth restricted ones.

Intrauterine growth restriction (IUGR) is associated with important maternal and perinatal morbidity and mortality. IUGR is typically secondary to defective oxygenation, leading to placental insufficiency.

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.

a fetal MRI in the pediatric radiology department of Necker-Enfants Malades Hospital or Robert Debré Hospital, for fetal or placental indications as part of usual workup, will be invited to participate in this protocol. At the waning of the scheduled fetal MRI, patients will subsequently receive an additional BOLD and ASL sequence before and after maternal hyperoxygenation.

Patients will be included in three centers : Necker Hospital, Robert Debré Hospital and Louis Mourier Hospital. Only at Necker Hospital: a subgroup of patients will be included at the beginning of the protocol for the adjustment of the settings of the MRI machine, for the determination of BOLD sequences' parameters, as well as the selection of the most adapted type of oxygenation mask.

In the three centers, investigators will include patients with IUGR fetuses and patients with a eutrophic fetus.

A total of two visits (selection visit and baseline) are scheduled for all patients in this trial. Patient selection will be done during a ultrasound visit. Patients can give their consent on the same day or on the MRI appointment day; in all cases the consent will be signed on the day of the appointment MRI.

The flow and duration of the oxygenation of the initial group "test patients" will be determined before completion of the examination; for other patients, the flow rate will be determined based on the results of this first group.

The duration of the BOLD sequence will be around 10 minutes. The sequences will focus on the feto-placental unit.

A first BOLD sequence will be launched under ambient air. The second BOLD sequence will be repeated after 5 minutes of maternal hyperoxygenation.

MRI data will be saved and analyzed at the Laboratory of Imaging Research of the team 2 of Paris Cardiovascular Research Center (INSERM U970).

The data necessary for the statistical analysis of the study are collected from the medical file of patients included in the study. Data entry will be performed by a research technician on electronic media via an internet browser.

The inclusion period will be of 57 months. Each woman's duration of participation will be 1 hour. The maximum duration of the study will be 57 months.

Inclusion Criteria:

• Major patient
• Patient with a singleton pregnancy
• Patient between 18 and 37 gestational weeks
• Informed consent signed by the patient
• Patient affiliated to a social security scheme (beneficiary or assignee) Specific criteria for patients with a eutrophic fetus
• Patient with fetal eutrophic on sonographic fetal weight estimation Specific criteria for patients with an IUGR-fetus Patient with a fetus presenting intra-uterine growth restriction diagnosed by ultrasound (<5th percentile).

Exclusion Criteria:

• Patient with the usual contra-indications for MRI
• Patient with an abdominal circumference> 125 cm
• Patient with a multiple pregnancy
• Patient with placenta accreta or percreta
• Patient with a pregnancy after long history of infertility and medically assisted procreation