Can humans reproduce in space? The short answer is that we don’t know. The long answer is perhaps, but there are significant barriers to making zero-gravity pregnancy safe, and research on the subject is just beginning.
Space is a dangerous place. Astronauts in peak physical condition often return home after long stays in space weak, with atrophied muscles and damaged eyes. Many of these effects are reversible, but some are not, such as doses of solar radiation they receive that can cause cancer later in life.
A significant part of the experiments on the International Space Station was designed to advance medical science and mitigate the worst of these problems. But there is more to learn, and when it comes to pregnancy, we know very little.
What we do know is that the real danger to the developing human embryo is not radiation: it’s gravity. Or rather, the lack of it. Early in the process, when cells begin to divide and grow, growth may occur more rapidly at one end of the embryo than at the other, and there is some evidence that gravity plays a role in this asymmetry.
Later, gravity helps to ensure the body forms correctly, with the cells oriented properly and in the right places. It is unclear what would happen to the developing human embryo in microgravity.
As in other areas of medicine, animal testing can help scientists understand the processes at work without risking human life. The first tests, dating back to the days of the Gemini program, were carried out with frog eggs. The researchers found no anomalies in cell division – a good sign.
Soviet scientists attempted tests of fertilization in fishbut they had trouble getting them to mate — it wasn’t until spaceflight in 1994 that they were successful in hatching fish in space, and even then, only specific species seemed to adapt well to microgravity.
Additional research in the 1990s found that 81% of embryonic newts born in space developed malformations of the neural tube – but this was reduced to 23% when the newts were placed in a centrifuge, creating artificial gravity at 1G.
Birds and geckos have also been studied, but if we really want to understand human development in space, we need to study mammals.
litters of young mice and rats studied in microgravity offer good news and bad news. The good news is that many perfectly healthy rats and mice survived their space flights and then adapted to life on Earth without any problems. Feared defects – changes that could last generations – did not materialize.
The bad news is that some litters showed harmful effects, but it is not yet known whether the cause was microgravity, or poor maternal care, as the mother behaved differently in microgravity and was unable to bond with her offspring as she would on Earth. This lack of parental care could explain the defects as easily as the lack of seriousness. More research is needed.
Two possible solutions
Human development depends to some extent on embryonic stem cells: versatile cells that can develop into any type of cell the body needs. Unfortunately, there is some evidence that this process can be hampered in space. That’s bad news for the prospect of pregnancy in space.
On that front too, however, it’s not all bad news. Stem cells from adult tissues – often used in treatments for degenerative diseases – actually appear grow faster in microgravitypotentially allowing for better availability of these treatments to those in need.
In the long term, for safe reproduction and pregnancy in space, advances are needed in two ways: we can attack the problem from an engineering point of view, and develop space habitats swivels that mimic 1G with artificial gravity; or, from a medical point of view, we can find ways to help the embryo develop at the cellular level, perhaps through drug treatments.
For now, Earth’s gravitational well (and perhaps other gravitational wells such as Mars) are the safer havens for pregnancy and I leave. Getting out of the proverbial cradle will not be a trivial matter. In this case, ‘Mother Earth’ is a fitting embodiment of our planet, as it is only here that our reproductive systems have evolved to function, and taking our biology beyond that will require creative adaptation, both technological and medical, to have hope. Of success.