A potential breakthrough in the world of reproductive medicine is looming.

Scientists in Japan are building a microfluidic chip to nurture the first stages of pregnancy. Eventually, they hope to create a fully automated artificial uterus in which egg and sperm are fed in at one end and an early embryo comes out on the other end, ready for implanting in a real mother.

Teruo Fujii of the University of Tokyo in Japan and his colleagues said using such a device could improve the success rate of in-vitro fertilization.

But other scientists say there is still a long road ahead. “While there have been many advances in the production of in-vitro embryos, these embryos are still sub-optimal (compared) to their in vivo counterparts,” said Matt Wheeler, of the University of Illinois in Urbana-Champaign, in a news release.

Wheeler, who is also working on automated IVF systems, said scientists first need to overcome the problem that, during IVF, eggs or embryos are often moved or washed with culture fluid, causing changes in temperature and pH.

To overcome these problems, Fujii’s team has created a tiny “lab on a chip” in which up to 20 eggs can be fertilized and then grown until they are ready for implantation. Endometrial cells, which line real wombs, are also grown in the device so that the chemicals they produce can reach the embryos and help them grow.

“We are providing the embryos with a much more comfortable environment, mimicking what happens in the body,” Fujii said in a news release.

Experiments in mice suggest that the chip is more successful than traditional IVF at producing embryos that will grow into healthy fetuses. Of 50 fertilized eggs grown on the chip, 30 developed into early embryos, compared to 26 out of 50 fertilized eggs grown through “microdrop” IVF.

During the microdrop process, mineral oil is used to cover the fertilized egg and a small volume of culture fluid is used to stop the egg from drying out.

In a separate experiment, Fujii’s team implanted embryos grown on the chip into mice and found that 44 percent of them developed into healthy fetuses, compared to 40 percent of those grown in microdrops. “It’s not just about more embryos surviving to be implanted, they also seem to be doing better once they are implanted,” said Wheeler.

The results were presented at a meeting in Lyon, France, in July. Fujii’s team has approval to test the device on human embryos and will do so later this year.

The chip could also be used for growing genetically modified animals, stem cells and cloned embryos, he added.