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Non-invasive imaging of placental circulation - Dr. Reut Yalon

During the course of pregnancy, a large degree of vascular remodeling must occur to support and maintain the functionality of the pregnancy. A crucial adaptive change to support the growing fetus/fetuses is the development of a functional placenta together with a sufficient maternal blood supply of water, ions, respiratory gases and nutrients. Normal fetal growth is dependent on proper maternal circulation, efficient exchange within the placenta, and appropriate architecture and function of the fetal vasculature system. Proper performance of all three components, namely the utero-placental-fetal unit, is necessary to ensure the well-being of the fetus, and pathological development in one or more of these utero-placental-fetal components can lead to a variety of prenatal syndromes, including intra uterine growth restriction (IUGR), preeclampsia, and fetal death in utero. In this PhD work we enhanced the understanding of the vascular network of utero-placental-fetal unit, thereby revealing basic biological principles underlying the robustness of pregnancy.

We studied the maternal uterine vasculature system, characterizing maternal-to-placental arterial exchange and the relative contribution of uterine vs. ovarian blood supply, revealing new concepts in the structure and function of the complex architecture of the uterine maternal vasculature in multi-fetal pregnancies. We provided a comprehensive description of placental function, resolving multiple placental compartments and characterizing them in their fractions and diffusion/flow characteristics, uncovering structural and dynamic aspects of in vivo placentas. Finally, we examined the spatial and temporal effects of transport of oxygen across the placenta and into the fetal circulation, characterizing the functional properties of maternal-fetal oxygen exchange via the placenta.

In each of these aspects a novel imaging approach was developed to help us address these issues in a non-invasive manner, which may provide essential research tools in the area of placenta development and function, some of them can potentially have clinical relevance.

Figure 1 | MIP angiography (red) overlaid on a coronal anatomical image, highlighting the maternal blood vessels and all of the placentas, without the injection of contrast agnet.