Untangling the way blood from mom & baby meet in the placenta

When you’re pregnant, your baby completely depends on the blood bond with you.

The connection is so vital that spotting irregularities in the flow across the placenta could be crucial for detecting fetal distress.

Unfortunately, there isn’t any method 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 currently-available MRI methods are not suitable. Problems with the technique come from things like motion of the baby in utero, the mothers’ breath, the varied structure of placental tissue, and the tangled maze formed by maternal and fetal blood vessels.

Blood in the placenta - Fluid-filled structures in the placentaIn a study in mice, conducted with advanced MRI methods, Weizmann Institute scientists have revealed — in unprecedented detail — the dynamics of the flow of fluids within the placenta.

Blood in the placenta: 3 different structures

As reported in September 2014 the Proceedings of the National Academy of Sciences, (PNAS), USA, they managed to identify three different types of fluid-filled structures: maternal blood vessels, which account for two-thirds of 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.

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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.

This technique could be particularly valuable when fast decisions about inducing labor need to be made, for example, when there are complications of pregnancy, such as preeclampsia or placental abruption.

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