It was 1983, and NASA was set to make history as Sally Ride prepared to become the first American woman to fly to space. The clock was ticking, but one final obstacle stood in the way of the meticulously planned mission. A crew of brilliant NASA engineers, some of the brightest young men in the nation, were completely stumped. Their issue wasn’t the rocket, the payload, or the orbital trajectory—those things were trivial. The problem was…tampons?
Ride’s rocket took off successfully, but if the NASA engineers had had it their way, dozens upon dozens of extra tampons would have followed her. “They asked, ‘Is one hundred the right number?’” Rider later recalled. The flight was only six days long.
“No,” she responded, “that would not be the right number.”
This episode went viral a few years ago, racking up millions of views across Twitter, YouTube, and TikTok. Ride’s story speaks to something that all women can attest to: Women’s reproductive health has long been mysticized and stigmatized in male-dominated spaces. Spaceflight is the quintessential example.
We’ve come a long way since Ride’s trailblazing trip; in the intervening years, a total of ninety-two women have flown to space. Progress has been made. However, our understanding of women’s health in space still lags far behind.
When people are sent up into space, there are an enormous number of factors that come into play: astronauts must contend with the dizzying G-forces of a rocket launch, harmful cosmic rays from deep space, and the long-term health consequences of living in zero gravity, just to name a few. And there are unique effects on the female reproductive system—dangers and potential changes that are severely understudied.
Now, understanding these effects matters more than ever. As astronaut training programs become more equitable and the private space industry dramatically increases the speed of manned rocket launches, more female astronauts are traveling to space than ever before. Additionally, with expeditions to the Moon, Mars, and beyond on the horizon, female astronauts must prepare for even longer and more arduous journeys in space. Finally, the prospect of colonizing other worlds raises the challenge of reproduction in space.
However, scientists are up to the task, using innovative techniques to study the impacts of space on the female reproductive system. Recently, a group of twenty-two forward-thinking doctors and space health researchers came together to collate their findings in a review article.
Effects of Radiation
As humans travel further beyond Earth, new threats and challenges are coming into focus. “The most important aspect [to consider in space travel] is radiation. DNA damage can cause cancer, cause mutations to the gametes, and cause other problems,” said Murat Basar, a contributing author and associate research scientist at the Yale School of Medicine who specializes in obstetrics and gynecology, reproductive endocrinology, and infertility. On Earth, we’re protected from radiation by Earth’s magnetic field, which deflects most charged particles that could harm us. However, outside of Earth’s protective blanket, we’re left vulnerable to all sorts of health effects from radiation. The average American experiences about 6.2 millisieverts (mSv) of radiation per year, but in space, radiation is unavoidable—NASA limits the lifetime exposure of their astronauts to six hundred mSv.
Women haven’t made enough trips beyond Earth’s magnetic field to accurately test the effects of radiation on their reproductive systems. However, scientists have looked for clues elsewhere, studying the impacts of radiative medical procedures. One such procedure is external beam radiotherapy (EBT), which aims to kill cancer cells using radiation. EBT is a highly targeted procedure—radiation is directed toward specific parts of the body at a controlled frequency for a very brief amount of time. However, despite all these precautions, EBT can still cause extremely harmful side effects, killing eggs, contributing to malfunctions in the ovaries, or causing premature menopause. Even just one EBT treatment can create life-long complications.
Radiation in space is much, much worse. There, radiation exposure is chronic, uncontrolled, and impacts the entire body. This kind of radiation is said to have high Linear Energy Transfer (LET), a measure of how much energy is deposited in matter over time. High LET radiation can cause dense ionization, and this results in significant damage to any living tissue or biological material it travels through. Considering that even minor molecular changes could be lethal for a developing cell, it is critical to understand the effects of this prolonged radiation exposure in space.
Circadian Rhythm Changes
Another factor at play is the effect of space travel on the body’s circadian rhythm. Circadian rhythm is a biochemical clock that regulates how our bodies release hormones, oscillating between different physiological states over the course of a day. Humans have a circadian rhythm that lasts just over twenty-four hours, matching the rising and setting of the sun. However, without the regular time-keeping mechanism of light, the circadian rhythm can break down, impacting the body in innumerable ways.
The rigors of space travel can cause such a breakdown easily: already, astronauts on the International Space Station, orbiting Earth at 17,500 miles per hour, must contend with a ninety-minute day, which means they experience multiple sunrises and sunsets within a single twenty-four-hour period. If humans ever wish to survive for long periods of time in deep space or on other planets, we will have to deal with radically altered cycles of day and night.
In addition, astronauts experience different amounts of gravitational acceleration. During a rocket launch, astronauts are slammed back into their seats, in a state of heightened acceleration called hypergravity. In an orbiting spacecraft, astronauts feel weightless, in a state called microgravity or zero-G. Both are capable of interfering with genetic processes that regulate circadian rhythms.
The genetic expression of the circadian clock is central; because it happens over a large area of tissue, the proper functioning of these genes is vital for the overall circadian system. However, some of these genes are also locally focused in reproductive organs and are heavily affected by the changes in sleep patterns that occur as a result of the nature of an astronaut’s mission. In fact, one of the key hormones at play is insulin, which helps regulate gene expression in the ovaries. Recent studies have shown that sleep deprivation, insomnia, and other disturbances to the circadian rhythm can cause insulin resistance, a phenomenon in which genes no longer respond properly to the hormone. The downstream effects can be massive, leading to infertility or health risks during pregnancy. Additionally, disruptions to the circadian rhythm can compound other already dangerous risks to the reproductive system. The circadian rhythm is linked to DNA repair mechanisms, which impact an individual’s cancer risk. Therefore, a female astronaut’s chance of developing cancer—already increased from radiation exposure—could be heightened even further.
Conclusion
Now that the harmful impacts of space on the female reproductive system are coming into focus, scientists are beginning to look for solutions. “With recent advances in the space industry, there are lots of new opportunities. To survive space, we need the ability to reproduce—especially as we think about expeditions to Mars and beyond,” said Cihan Halicigil, a contributing author and an assistant professor of obstetrics, gynecology, and reproductive sciences at the Yale School of Medicine.
In the last few years alone, scientists have made leaps and bounds in the field. For instance, using a 3D printer, scientists were able to create copies of mice ovaries in order to probe how their tissues and hormones respond to the rigors of space. Furthermore, scientists are getting better and better at replicating microgravity on Earth, making in-depth studies of its effects on the body much easier. Finally, the advent of remote surgery has made medical care accessible in remote locations, creating hope that advanced medical procedures might be carried out in space.
As humanity enters a brave new era of space exploration, these discoveries and innovations will help make travel to the stars accessible to all, regardless of sex.