The new system, described in a report released today by Nature Communications, attempts to mimic fetal life in the uterus as closely as possible. It differs from previous models in three ways: circulation is powered by heartbeat, oxygen and nutrient exchange take place through the umbilical cord and, in major contrast to an incubator, breathing continues to take place in a fluid environment, by way of amniotic fluid created in the lab.
“Fetal lungs are designed to function in fluid, and we simulate that environment here, allowing the lungs and other organs to develop, while supplying nutrients and growth factors,” Marcus Davey, a member of the research team, said in a statement.
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By maintaining the amniotic fluid, the system eliminates the need for a ventilator, which Flake says can arrest the development of lungs while pumping in atmospheric oxygen that underdeveloped lungs may not be prepared to breathe. This air could also contain pathogens. Instead, in the new system, the infant remains connected, via their umbilical cord, to an external, low-resistance machine that would substitute for the mother’s placenta, exchanging oxygen and carbon dioxide in the blood while providing nutrients.
In addition, all circulation inside the near-sterile space would be driven by the fetal heartbeat, reducing pressure that could overload an underdeveloped heart.
While previous research has explored the use of an artificial placenta in animal models, systems without a pump have extended the extra-uterine period by a mere 60 hours. In these studies, the animals sustained brain damage. The system developed by Flake and colleagues, in contrast, showed no adverse effects and kept some of the lambs’ health for 670 hours — the equivalent of 28 days.
In the United States, any birth that takes place prior to 37 weeks of gestation is considered to be premature. Of these, one in 10 tends to be “critically preterm,” or less than 26-weeks-old. These are the cases of greatest concern, as extreme prematurity is the leading cause of infant mortality and morbidity in the country. Currently, one-third of all infant deaths and one-half of all cases of cerebral palsy are attributed to prematurity.
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Currently technology has increased the overall survival of infants born with as little as 22 or 23 weeks of gestation, but such scenarios often come with life-impacting effects. At this age, the rate of survival is quite low — between 30 and 50 percent — while survivors have a 90 percent risk of morbidity from chronic diseases and complications attributed to under-developed organs. Infants born at 28 weeks, by comparison, evade the most severe outcomes.
This is the critical five-week gap that Flake and his colleagues are hoping to bridge. They have no intention of extending the viability of premature infants born beyond the current threshold of 23 weeks, prior to which the risks would be “unacceptably high,” according to Flake. While it may be a decade before such a device will be on the market, he is optimistic that if realized, it would mark a vast improvement over the currently available technology.
“This could establish a new standard of care for this subset of extremely premature infants,” Flake said in a statement.
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