A view of a fetus in an artificial womb, 1965.
Researchers successfully nurture extremely preterm lamb fetuses outside a natural womb. Photo: Fritz Goro
If you live for about 80 years, your nine months in the womb will represent less than 1% of your time on Earth. But those nine months represent a crucial period for growth and development.
Sometimes, though, babies are born before they get those nine full months in utero. And while the accepted protocol is to place premature infants in an artificial incubator — protecting the baby from infection and maintaining temperature and humidity — soon there may be better options.
Researchers at the University of Western Australia and Tohoku University Hospital are testing artificial wombs: plastic bags filled with synthetic amniotic fluid and connections for placenta-based life support. The team recently revealed in the American Journal of Obstetrics and Gynecology that they have successfully sustained premature lamb fetuses using their artificial wombs.
“We have proven the use of this technology to support, for the first time, extremely preterm lambs… in a stable, growth-normal state for five days,” said senior author Matthew Kemp in a statement from Tohoku University Hospital.
This research may help treat preterm human babies in the near future. According to the Lancet, nearly 15 million babies around the world were born preterm in 2014. Preterm or premature babies are not simply undersize or underweight—they are underdeveloped in very important ways. Often, their lungs are too small and their hearts not strong enough to function properly. This is especially true if a premature human baby is born at 28 weeks or earlier, which makes them extremely preterm. At this point, they still need gas and nutrient exchange through the placenta in order to grow, which means it’s hard for them to live on their own.
Making an artificial womb function like a natural womb isn’t easy. Not only do the fetuses need to be safe, but they also need life support and the right combinations of nutrients so they don’t develop infections or brain injury. The goal is also to promote the same growth and cardiovascular function that develops in a natural womb.
Existing artificial incubators are already emotionally difficult to deal with for parents. Infants in bags of fluid may be even harder to accept.
Kemp’s group was able to support and promote growth and development in extremely preterm lamb fetuses inside an artificial womb for 120 hours, or about five days. The lamb fetuses didn’t show any signs of infection, inflammation, or brain injury.
A different research group, based at the Children’s Hospital of Philadelphia, published results of a similar experiment in Nature Communications in 2017, in which they supported lamb fetuses in artificial wombs for up to four weeks. The team demonstrated successful life support for lamb fetuses that were 105 days old.
Kemp’s group also tested their artificial womb on lamb fetuses that were 95 days old, the youngest fetuses so far. That’s equivalent in size and weight to a 24-week-old human fetus. Starting with a lamb fetus in an artificial womb 10 days earlier than previous experiments means the fetus is developmentally that much more premature—and that could make survival much more difficult. For an experiment that lasted only five days, it’s unclear how long this system could successfully support a lamb or a human fetus and if it can ultimately increase survival.
Experts are concerned about how this kind of research will translate to actual practice. Claire Roberts of the University of Adelaide reviewed the Nature Communications paper and wrote a commentary in Nature warning that although lambs may not show brain injury, human brains develop differently. Roberts also made the point that existing artificial incubators are already emotionally difficult to deal with for parents. Infants in bags of fluid may be even harder to accept.
Others have commented on the potential ethical questions around abortion, asking whether this kind of work could affect abortion policies. If this research progresses to the point where human fetuses even younger than 24 weeks can be supported in artificial wombs, that may change when a fetus is considered viable, which in turn could affect the cutoff point for the fetus age when abortion is legally acceptable. State laws vary in the United States, but many prohibit abortion after 20 to 24 weeks into a pregnancy.
But the goal of this field of research has never been to completely replace a natural womb. It aims to create a space outside the natural womb where preterm babies can continue to grow and develop safely until they can survive in the outside world. And though the research is progressing, an artificial womb for human use won’t be usable anytime soon.
“Based on data presently publicly available, there are many years of work remaining before it will be possible to justify using technology of this nature in the clinic,” Kemp says.