Maybe Elton John was right when he sang in his hit “Rocket Man” that “Mars ain’t the kind of place to raise your kid.” As humanity moves closer and closer to astronauts and colonists living off of the Earth, pregnancy and childbirth are inevitable. A new study looks at the subject and it raises some interesting risks as well as a call for more research.

Published February 3 in Reproductive BioMedicine Online, a new review, “Reproductive biomedicine in space: implications for gametogenesis, fertility and ethical considerations in the era of commercial spaceflight,” brings together nine international experts in reproductive health, aerospace medicine, and bioethics to consider the issue.

Their central finding is stark: despite more than 65 years of human spaceflight, remarkably little is known about how the space environment affects the reproductive systems of men and women during long-duration missions.

“More than 50 years ago, two scientific breakthroughs reshaped what was thought biologically and physically possible — the first Moon landing and the first proof of human fertilisation in vitro,” said lead author Giles Palmer, a clinical embryologist at the International IVF Initiative. “Now we argue that these once-separate revolutions are colliding in a practical and underexplored reality.”

Three Potential Threats

The review identifies a triad of hazards. Cosmic radiation is the most well-characterized: beyond Earth’s protective magnetosphere, astronauts are exposed to galactic cosmic rays and high-energy charged particles that current shielding cannot fully block.

Doses exceeding approximately 250 milliSieverts can disrupt sperm production, and chronic exposure may impair the hormonal signaling that governs testosterone and sperm quality. (The average dose on ISS is 13 to 27 millisieverts (mSv) per month.) For women, animal studies link radiation to menstrual disruption and elevated cancer risk, though reliable human data from long missions remains scarce.

Microgravity introduces a separate set of problems. Weightlessness removes a fundamental mechanical cue that influences hormonal regulation, gamete development, and early embryonic growth. Animal studies have shown decreased sperm motility, increased DNA fragmentation, and disrupted development under microgravity conditions. Notably, a complete mammalian reproductive cycle — from egg and sperm development through birth — has never been achieved in space.

Circadian disruption rounds out the triad. Astronauts on the ISS experience roughly 16 sunrises every 24 hours. On Earth, similar disruptions in shift workers are linked to menstrual irregularities, reduced fertility, and poor pregnancy outcomes. The molecular clock genes active in reproductive tissues are known to impair ovulation when thrown out of sync.

Data from the Space Shuttle era offers some reassurance: female astronauts’ subsequent pregnancy rates were comparable to age-matched women on Earth. But those missions were far shorter than what’s now planned for lunar and Mars exploration, and male reproductive outcomes in space remain poorly documented. Clearly, more study is needed.

Ethical Questions Remain

The review raises ethical questions that reach beyond medical risk. If a child were conceived and born under lunar or Martian gravity, their skeletal and muscular development would differ fundamentally from Earth-born humans. Such an individual might be physically unable to live under terrestrial gravity — a scenario the authors frame as one of the most profound considerations of the coming era.

“As human presence in space expands, reproductive health can no longer remain a policy blind spot,” said senior author Dr. Fathi Karouia, a research scientist at NASA. He called for international collaboration to close knowledge gaps before commercial and long-duration missions make these questions unavoidable.