Spaceflight may harm the reproductive system of astronauts' kids and grandkids, early mouse study suggests

Lab mice who spend time in space seem to bear offspring with reduced reproductive capacity, a new study suggests.

But what that might mean for human astronauts and their families is still unclear.

The research, published June 30 in the journal PNAS , looked at female mice that had spent extended periods on the International Space Station (ISS).

These mice had similar levels of fertility as Earth-bound mice.

However, their children and grandchildren produced smaller-than-average litters, had fewer litters overall and had lower levels of key reproductive hormones, among other measurable differences.

"The offspring of those that came back from space were altered in their behavior, their muscle, their ability to reproduce further," study co-author Lane Christenson , a professor of cell biology and physiology at the University of Kansas Medical Center, told Live Science.

And "just about every marker we looked at had some differences." As the study was conducted in mice, it’s difficult to determine whether the effects might carry over to human astronauts.

However, mice are good biological models for understanding the health impacts of space travel, given that they are mammals with a similar reproductive system to humans, experts told Live Science.

As scientists explore the feasibility of long-term space travel, this study highlights the need for further research on the impact of long-term spaceflight on the reproductive system, the study authors argue.

A "void" in research Past research, such as the NASA Twins Study , has suggested that short-term spaceflight has modest effects on human health .

That study compared astronaut Scott Kelly , who completed a year-long mission on the ISS, to his identical twin brother, Mark Kelly, who remained on Earth.

However, few studies have explored the long-term health impacts of spaceflight, including those that might affect reproduction.

A 2019 study looked at male mice that spent time aboard the ISS and found they could father healthy offspring.

The new study, by contrast, was conducted to "fill a void" in research investigating how space travel might impact the female reproductive system, Christenson said.