Recently, scientists at the Center for Fetal Research in the Center for Fetal Diagnosis and Treatment at Children’s Hospital of Philadelphia reported that they had successfully raised eight prematurely born lambs in an artificial womb for 28 days. But how did they do it? Actually, it’s not as complicated as it seems.

The system uses a circulatory system, a closed fluid environment, and the fetus’ own heart to pump blood, to support a stable development. Blood pumped by the fetus’ heart is circulated through an oxygenator and back to the fetus, similar to the gas exchange across a placenta. A very specially made fluid mimicking amniotic fluid fills the womb, and is continuously exchanged, similar to how it is in the uterus. The fluid provides insulation, protects the fetus from infection, and helps maintain temperature, pressure, and light. The fluid is also very important in lung development.

The system worked very well. After four weeks in the artificial womb, all the lambs showed normal statistics in circulation, blood pressure, metabolic processing, growth, lung development, and brain development. Seeing these positive results raises a question: Will this technology be able to be used for premature human babies?

The hope is that it will eventually be used for humans, but it won’t be soon. Scientists still need to scale down the system to the size of a human fetus and find a good fluid to mimic human amniotic fluid, as well as refine the system to have the results compare to current neonatal intensive care treatments. Other treatment options for premature birth also discovered with sheep models, such as steroid injections used to help accelerate lung development, took over 20 years to get into clinical practice. When it does finally get implemented, though, the plan is to use it to get babies to 25 weeks, when there is about an 80% life expectancy, which is much higher than the near zero at and before 22 weeks. All of this will hopefully meet the unmet need of extreme prematurity.