Fetal growth restriction (FGR) is a serious complication of human pregnancy where the fetus fails to reach its genetically pre-determined growth potential. It is a common condition, affecting 5 -15% of all pregnancies (Gardosi 2009) and is linked to a third of all antepartum deaths (CEMACH 2008). An ongoing problem for obstetricians is the difficulty in diagnosing and predicting FGR and those at highest risk of poor outcomes. Placental insufficiency is a major cause of FGR and specific abnormalities in placental morphology and function occur in this condition; constituting an abnormal FGR placental phenotype (Sibley, Turner et al. 2005). Magnetic Resonance Imaging (MRI) is a powerful tool that allows quantitative analysis of several indices relating to tissue structure and function and, therefore, is of potential use in identifying this phenotype. We hypothesised that a range of MR indices would be feasible in the placenta at 1.5 T, that these indices would be altered in FGR and that there would be correlations with relevant parameters of placental morphology. Ultimately, we aimed to assess whether these indices could be used in the assessment of FGR in utero.Using MRI we estimated placental volume, widths, length and depths in groups of women with normal and FGR pregnancies. We also measured placental relaxation times, T1 and T2, which relate to tissue composition and assessed parameters relating to blood flow using Intra-Voxel Incoherent Motion (IVIM) and Arterial Spin Labelling (ASL). We demonstrated an FGR placental phenotype that was reduced in volume but increased in depth, by around 10mm, with a shorter T2 relaxation time and lower values of D (the diffusion coefficient) measured by IVIM. A trend for reduced perfusion measured by ASL was observed in pregnancies with birthweights less than 10th centile (Gardosi, Chang et al. 1992). T2 and D also correlated with stereological indices of placental morphology.In conclusion, the studies in this thesis illustrate these MRI indices show great potential asbiomarkers for identifying the FGR placenta