Scientists have succeeded in creating synthetic mouse proto-embryos in the lab, in what is being heralded as “opening the black box” of pregnancy.

The team from Maastricht University and the Hubrecht Institute in the Netherlands made the embryos in a dish using stem cells, which could help solve what causes early miscarriages. The findings were published in Nature.

“Our research helps to understand the perfect path an early embryo must take for a healthy development,” lead researcher Dr Nicolas Rivron said in a statement.

In the experiments, bundles of mouse stem cells were used to initiate pregnancy inside mice wombs, without using sperm or eggs. While it did not lead to the creation of a real embryo, the fact that it started the process could reveal some information about the early phases of life.

Embryos are pretty hard to study as they’re incredibly small, about the width of a human hair, and located inside the womb. By creating these embryo-like structures, however, the team said they could help develop new drugs to deal with fertility problems.

"This breakthrough has opened up the black box of early pregnancy," Rivron told AFP. "[The embryos] will help us better understand the hidden processes at the start of life, to find solutions for fertility problems, and to develop new drugs without the use of lab animals."

Mammal eggs develop into blastocysts a few days after they have been fertilized, a spherical ball of around 100 cells that become the placenta and the embryo. This research marked the first time that the self-organization of these cells had been triggered, dubbed “blastoids”.

An interpretation of what a blastoid looks like. Green is the future placenta, and red is the future embryo. Nicolas Rivron

It’s hoped this could help work out how small flaws in the embryo develop, such as in some forms of diabetes. It could also reveal some aspects of infertility, and improve the chances of in vitro fertilization (IVF) treatments working.

“For the first time, it is now possible to form early model embryos in unlimited numbers that implant in utero [in the womb],” the statement noted.

At the moment, there aren’t any plans to try the results with human stem cells, with Professor Robin Lovell-Badge from the UK’s Francis Crick Institute – who were first to get approval to modify human embryos – telling BBC News that was “very remote”.

“This is a pity for basic research because it would be very useful to have a limitless supply of human blastocyst-like stage embryos,” he said. “However, it may come as a relief to others that such a method of producing many genetically identical human embryo-like structures that might be capable of implantation is not feasible.”

Still, for now, it’s a major breakthrough. And it might just solve quite a few issues relating to pregnancy.