Can Humans Get Pregnant in Space?

After watching a space documentary, reproductive biologist Nicole McPherson got a curious question from her husband on their drive to work: “Do you think humans could reproduce in space?”

“I immediately thought, ‘Oh yeah, of course,’” she says. But the more she considered it, the more complicated the question became. Human reproduction depends on countless environmental conditions shaped by life on Earth, making pregnancy and reproduction beyond the planet far less straightforward than it seems. “I kept thinking. Maybe we can’t,” she adds.

Space is a hostile environment for adult astronauts, let alone babies or pregnant people. Without pressurized spacecraft or spacesuits, astronauts can lose consciousness and die within seconds. Solar flares and galactic outbursts can release high-energy cosmic rays that cause DNA damage and cellular dysfunction. The lack of gravity can also lead to muscle and bone loss, increased cardiovascular risks, immune system dysfunction, and neurological issues.

The question might seem far-fetched, more sci-fi fantasy than biological reality. But as humans push the limits of living beyond Earth and prepare for long-term space missions to the moon and Mars, some scientists see human reproduction in space as inevitable.

“Eventually, people are going to get pregnant in space via accident [or deliberately], and you don't want to be surprised and say, ‘Oh, this person is pregnant in space, what's going to happen to the baby?’” says Douglas Ruden, a developmental biologist at Wayne State University in Michigan. “It would be nice to know [that] ahead of time.”

Despite the enormous risks, researchers are exploring how reproduction might work beyond Earth. They are testing pregnancy in model organisms, launching embryos in satellites and spaceships, running spaceflight simulations, and building new tools to understand how microgravity, radiation, isolation, and stress could affect fertility, fetal development, and long-term health.

(What toll does spaceflight take on astronauts? Here’s what we know.)

How Sperm and Egg Respond to Microgravity

McPherson and her team at Adelaide University in Australia recently looked at how sperm cells react to microgravity using a device called a clinostat, a random positioning device that stimulates space-like conditions where cells can’t tell which way is up or down. They tested whether human, mouse, and pig sperm could navigate a small maze mimicking the female reproductive tract within the clinostat to successfully fertilize eggs and lead to normal embryo development afterward.

While sperm moved normally, far fewer of them successfully reached the egg. Under microgravity simulations, the number of sperm that finished the maze dropped by 30 to 50 percent, the team reported in the journal Communications Biology earlier this year. The drop hints that gravity may normally help sperm orient themselves inside the reproductive tract, McPherson says.

Interestingly, when McPherson’s team added progesterone, a hormone naturally released near the egg in humans, sperm navigation improved. “If you’re giving them enough time, finally, they get to the other end,” she says. While fewer sperm succeeded, those that did appeared to be of higher quality too. Brief microgravity exposure caused some developmental changes, and longer exposure slowed embryo growth, reduced embryo quality, and led to fewer cells suggesting that the earliest stages of reproduction are especially vulnerable.

This experiment was among the first to test the impact of microgravity on human sperm and how they navigate microchannels mimicking the female reproductive tract. Studying human embryos comes with ethical constraints, which get even more dicey in space.

It’s Hard to Get Mice Pregnant in Space

For obvious reasons, NASA prohibits pregnant people from flying on space missions. Several astronauts have traveled to space, returned safely, and later had healthy babies, suggesting that spaceflight does not necessarily cause pregnancy complications. But studying pregnancy itself in space is far more complicated. “A grown-up female can decide for herself whether she wants to take part in an experiment, but the baby she's [carrying] in her body is not. That’s the reason it's a serious concern whether we want to do experiments with a human subject that cannot decide for itself,” says Marcel Egli, a mechanobiology scientist at the University of Applied Sciences and Arts in Lucerne, Switzerland.

While working with human embryos in the space environment brings ethical challenges, there have been various studies looking at embryo development patterns in several animals. Since 1965, several different animals, including geckos, rats, quails, clawed frogs, newts and zebrafish, have been taken to space to study about their reproductive and early developmental processes.

Even among mammals, “lots of experiments have been done over the last 40-50 years taking pregnant mice into space and [whether] they can give birth,” says Ruden. But the challenge is that the scientists hadn't gone through the entire cycle. “It's hard to get natural mating in space with mice. They get sick all the time, so they're not going to want to mate,” Ruden says.

How Embryos React to Low Earth Orbit

Still, some studies have hinted at how mammal embryos react to the environment of low Earth orbit. In one early 2000s experiment, researchers sent Norwegian rats to the International Space Station (ISS) in the middle of pregnancy; the rats returned to Earth a couple of days before they gave birth. The pregnant rats that flew to space had twice as many labor contractions compared to normal rats. Other parameters including labor length, number of babies and baby weight, to early maternal caring behaviors were essentially the same as rats on Earth.

In 2020, China launched a recoverable satellite, Shijian-10 (SJ-10), into space, carrying early-stage mouse embryos in an automated space nursery (basically a mini-incubator). The satellite was designed to operate autonomously without human intervention. It kept the embryos warm and stable, provided a nutrient-rich food for growth, periodically captured microscopic images to track development, and preserved the samples so scientists could study them later.

Once the scientists recovered the satellite, they found that development had continued: The embryos divided from a single cell into blastocysts, tiny hollow balls of cells that form before implantation in the uterus. However, only a small number developed into healthy blastocysts.

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Cosmic Rays May Be More Dangerous Than Microgravity

The SJ-10 embryos also pointed to impacts beyond the weightlessness of space. Their DNA had abnormal patterns of chemical changes around regions that turn genes on and off. While microgravity can alter DNA repair pathways, increase stress and accumulate damage over time, the patterns matched those of embryos on Earth exposed to low doses of electromagnetic radiation.

The DNA damage likely came from cosmic radiation, either high-energy particles from the sun or galactic cosmic rays that speed through space at extreme velocities. When cosmic rays impact something, they produce cascades of energetic particles and are extremely destructive. “You can think of cosmic rays as sort of like little tracks going through your body, causing localized cell damage. If you're exposed for years, it will have a cumulative effect,” says Arun Vivian Holden, an emeritus professor of computational biology at the University of Leeds in the United Kingdom. For a developing brain in this critical phase of life, the resulting damage could also build up over time, he adds.

On Earth’s surface, humans don’t have to worry about space radiation because the planet’s magnetic field extends into space and forms a protective bubble that blocks most rays. Spacecraft and satellites are often built with metal shielding and protective electronics to reduce exposure to lower-energy radiation during space travel. However, high-energy particles can still penetrate these shields and even trigger secondary particle showers when they strike the hull.

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Protecting Future Astronauts—Pregnant or Not—From Space Dangers

Conversations about pregnancy and space babies obviously raise important questions about safety in orbit. Cosmic rays (and other space hazards) pose a threat to all astronauts, especially as they spend more time beyond Earth’s protections. That’s why NASA is actively exploring new materials that can better shield astronauts from space radiation. One approach is passive shielding, placing protective materials between astronauts and incoming radiation, similar to how a lead apron protects patients during an X-ray.

Researchers are also testing other radiation-blocking options like filling spacecraft walls with water or using advanced layered materials such as boron nitride nanotubes (BNNTs), strong, hollow nanostructures made of boron and nitrogen atoms. Both store hydrogen, which helps absorb or scatter high-energy particles like neutrons and other ionizing radiation.

For now, pregnancy in space remains a distant theoretical possibility—but returning an infant to Earth might be just as challenging. If someone gives birth in weightlessness, the baby’s body will physically adjust to that particular environment. “The infant might adapt to develop less muscle and bone mass, because it's not needed. Babies’ whole circulation and blood pressure might adapt differently,” Egli says. The challenge however is to help them adapt back to the normal Earth or other planet’s gravity. “We would need a lot of infrastructure to create an Earth analog situation,” he adds.

McPherson argues that understanding the fundamentals of how reproduction works can lead to other applications. Understanding sperm navigation in complex environments could help improve IVF outcomes or assessments of sperm quality for agricultural practices. Many space research leads to advancement for Earth based tools too. “When you think about all the advancements in food packaging—from freezing, drying and storage—or even iPhone cameras, many of these have come from inventions made for space,” she says.

The work is not just about whether humans can reproduce in space, it is also about understanding the basic science of how humans are formed. “We see conception happen and embryos grow, and it’s wonderful, but we still don’t really understand the mechanical forces and molecular signals that drive the creation of an entire human being,” McPherson says. “That I think is the biggest perplexity we have in biology.”