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Imaging technique allows visual of blood flow across placenta

September 30, 2014
Weizmann Institute of Science
There is currently no reliable method for observing the blood flow across the placenta to detect fetal distress. Scientists have now revealed, in unprecedented detail, the dynamics of fluids within the placenta. They accomplished this by combining two MRI methods and a novel, ultrafast scanning approach: spatiotemporal encoding (SPEN).

The fetus in the womb is wholly dependent on the blood bond with the mother. Spotting irregularities in the flow across the placenta could therefore be crucial for detecting fetal distress, but no reliable method is currently available for monitoring the flow or detecting other signs of the distress in its early stages.

Magnetic resonance imaging, or MRI, can be safely performed during pregnancy, but today's MRI methods are not suitable, due to problems like the motion of the fetus or the mother's breathing, the varied structure of placental tissue, and the tangled maze formed by maternal and fetal blood vessels.

In a new study in mice conducted with advanced MRI methods, Weizmann Institute scientists have now revealed, in unprecedented detail, the dynamics of the flow of fluids within the placenta. This feat was all the more impressive given that a mouse placenta is around the size of a dime. As reported recently in the Proceedings of the National Academy of Sciences (PNAS), they managed to identify three different types of fluid-filled structures: maternal blood vessels, which account for two-thirds of the blood flow in the placenta; fetal vessels, which account for about one-quarter of the flow; and embryo-derived cells infiltrating the mother's vasculature, which account for the rest of the flow and in which the exchange of fluids between mother and fetus takes place. The researchers also found that in maternal vessels, blood flows by diffusion, whereas in fetal vessels, the flow, stimulated by the pumping of the growing fetus's heart, is much faster. In the cells that had infiltrated the mother's vasculature, the dynamics of the flow follows an intermediate pattern, driven by both diffusion and pumping.

Two sophisticated MRI methods were combined to enable the study: one geared toward monitoring diffusion, and another directed at identifying structures with the help of a contrast material. They could be applied successfully in large part thanks to an innovative scanning approach, spatiotemporal encoding (SPEN), a Weizmann Institute technique. Because SPEN is ultrafast and makes it possible to separately encode signals from such different materials as air or fat, it allowed the researchers to overcome disturbances created by movement and the variability of placental tissue.

If developed further for safe and reliable use in humans, this combined approach holds great promise as a noninvasive means of detecting fetal distress caused by disruptions in the placental flow. It can be particularly valuable when fast decisions about inducing labor need to be made; for example, with complications of pregnancy such as preeclampsia.

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Materials provided by Weizmann Institute of Science. Note: Content may be edited for style and length.

Journal Reference:

  1. E. Solomon, R. Avni, R. Hadas, T. Raz, J. R. Garbow, P. Bendel, L. Frydman, M. Neeman. Major mouse placental compartments revealed by diffusion-weighted MRI, contrast-enhanced MRI, and fluorescence imaging. Proceedings of the National Academy of Sciences, 2014; 111 (28): 10353 DOI: 10.1073/pnas.1401695111

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Weizmann Institute of Science. "Imaging technique allows visual of blood flow across placenta." ScienceDaily. ScienceDaily, 30 September 2014. <>.
Weizmann Institute of Science. (2014, September 30). Imaging technique allows visual of blood flow across placenta. ScienceDaily. Retrieved June 17, 2024 from
Weizmann Institute of Science. "Imaging technique allows visual of blood flow across placenta." ScienceDaily. (accessed June 17, 2024).

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