Methods to safely characterize placenta accreta, placental perfusion, and to molecularly profile the placenta in vivo, and longitudinally could greatly enhance our ability to study and treat placental dysfunction. Currently, a combination of ultrasound and MRI yields a sensitivity of ~85% for placenta accreta, yet, the consequences of a circumstantial finding at childbirth are profound, including massive obstetric hemorrhage, and often, a hysterectomy. Contrast-enhanced MRI (CE-MRI) is an obvious choice, but is currently not recommended due to the fear of fetal exposure to contrast agent. This study therefore evaluated a novel liposomal nanoparticle agent that does not cross the placental barrier, thus preventing fetal exposure [1].MR angiography (MRA) was performed on pregnant Sprague-Dawley rats, using both 1T permanent magnet and 9.4T cryo-cooled magnet. Conventional contrast agent (DotaremÒ, gadoterate meglumine) and a novel Gd-containing liposomal nanoparticle contrast agent with 100nm particle size, and long circulation half-life (~18 hours) were used for contrast-enhanced MRI [2]. A 3D GRE sequence was used for MR-angiography. Dynamic contrast-enhanced MRI (DCE-MRI) was performed to study the kinetics of contrast agent in the placenta, and systemic clearance. DCE-MRI was performed using a 2D-GRE sequence with the following parameters: TE=3.4 ms, TR=15ms, flip angle=70°, slice thickness=1.5mm, number of slices = 2, field of view=64 mm, matrix=128x128; scan time = 15 seconds. A total of 60 continuous scans were acquired (total time = 15 minutes) to collect the dynamic data. The contrast agent was administered (0.2 mmol Gd/kg dose) after acquisition of 5 baseline scans. DCE-MRI images were analyzed using the DCE@urLAB software for estimation of perfusion parameters [3]. MRA at both 9.4T and 1T using the liposomal contrast agent yielded exquisite images of the placental vasculature, including the penetrating arteries, the central arterial canal, and the placental labyrinth (Fig 1). DCE-MRI showed that the placental labyrinth fills first, followed by the decidual region of the placenta, consistent with previously reported flow dynamics in both rodents and humans. While gadoterate meglumine showed detectable enhancement in the fetus, the liposomal agent showed none. Kinetic analysis showed the delayed enhancement of the maternal decidual region, following immediate enhancement of the placental labyrinth. Rapid clearance of the gadoterate meglumine from the systemic circulation, and extremely slow clearance of the liposomal contrast agent were also demonstrated. Post mortem ICP analysis of the placenta and fetus demonstrated non-permeation of the liposomal agent through the placental barrier, while gadoterate meglumine appears to readily cross the barrier.The study demonstrates the feasibility and utility of a liposomal gadolinium nanoparticle contrast agent for placental imaging.