Placental MRI Predicts Fetal Oxygenation and Growth Rates in Sheep and Human Pregnancy

Magnetic resonance imaging (MRI) assessment of fetal blood oxygen saturation (SO(2)) can transform the clinical management of high‐risk pregnancies affected by fetal growth restriction (FGR). Here, a novel MRI method assesses the feasibility of identifying normally grown and FGR fetuses in sheep and is then applied to humans. MRI scans are performed in pregnant ewes at 110 and 140 days (term = 150d) gestation and in pregnant women at 28(+3) ± 2(+5) weeks to measure feto‐placental SO(2). Birth weight is collected and, in sheep, fetal blood SO(2) is measured with a blood gas analyzer (BGA). Fetal arterial SO(2) measured by BGA predicts fetal birth weight in sheep and distinguishes between fetuses that are normally grown, small for gestational age, and FGR. MRI feto‐placental SO(2) in late gestation is related to fetal blood SO(2) measured by BGA and body weight. In sheep, MRI feto‐placental SO(2) in mid‐gestation is related to fetal SO(2) later in gestation. MRI feto‐placental SO(2) distinguishes between normally grown and FGR fetuses, as well as distinguishing FGR fetuses with and without normal Doppler in humans. Thus, a multi‐compartment placental MRI model detects low placental SO(2) and distinguishes between small hypoxemic fetuses and normally grown fetuses.