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  • {♫Intro♫}

  • Will we ever live in space long-term?

  • Prominent scientists have argued that the future of our species could lie off-world.

  • But there's one thing we'd need to make that work: babies.

  • It's not just about parentingsurely our intrepid astronauts would be up to that challenge.

  • It's that some of them would eventually have to get pregnant in the first place.

  • As wild as it sounds, researchers are already trying to figure out if people can make space

  • babiesbut so far, the results don't look great.

  • One major hurdle is the lack of gravity.

  • That includes near-weightlessness, or microgravity, as well as places with less gravity than our

  • home planet

  • like Mars, where gravity is less than half of what we're used to.

  • Most experiments that have tried to shed light on this have been done in real or simulated

  • microgravity, so that's what we'll focus on here.

  • But so far, scientists think that even Martian gravity would pose problems for conception

  • and gestation.

  • Overall, the story starts out okay: Menstruation in space seems to work normally, at least

  • for short tripsastronauts often choose to skip their periods for longer missions.

  • So although we don't know for sure, that suggests that ovulation would also happen normally.

  • Meanwhile, sperm seem to fare, well, kind of okay in microgravity.

  • Like, in 1979, researchers flew live rats on a research satellite for eighteen days.

  • And when they got home, they successfully mated with ovulating rats.

  • Except not all of their offspring were totally healthythe growth and development of

  • babies fertilized by mature sperm that were exposed to zero-g effects lagged behind control litters.

  • The nice thing is, we might be able to get around this by using space sperm banks instead.

  • FST01 In research presented in 2019, scientists

  • in Barcelona reported some preliminary evidence that frozen human sperm can survive short

  • bursts of microgravity with no ill effectsthough their evidence came from specialized

  • aircraft, not from space.

  • Still, it's a start.

  • Now, having healthy cells is one thing, but to get a fetus, an egg needs to be fertilized.

  • And there is evidence that sperm can fertilize eggs in microgravity.

  • One 2009 study used a spinning machine to simulate microgravity, and successfully carried

  • out in vitro fertilization using mouse sperm and eggs.

  • But even then, fertilization is still a step or three away from pregnancy.

  • Pregnancy isn't official until an embryo can implant into its host's uterine wall.

  • For that, you need the formation of the blastocyst — a hollow, fluid-filled ball of cells that

  • forms within a few days of fertilization.

  • The layer of outer cells is called the trophoblast, which helps the embryo to burrow into the

  • uterine wall and form the placenta.

  • There's also a clump of inner cells called the embryoblast, which gives rise to the fetus itself.

  • And it seems like embryos might be able to do all that in space.

  • Although it hasn't been reported in a peer-reviewed journal, an experiment containing mouse embryos

  • that flew on China's first microgravity satellite saw some of them form blastocysts.

  • Which is promising, but we'll need more studies to confirm.

  • But even if blastocysts can form in space, it's unclear whether they could implant

  • and keep growing.

  • In that same 1979 mission we mentioned, male and female rats were also sent into orbit

  • and allowed tomingle.

  • Some of them did get pregnant, but none of them gave birththe researchers believed

  • that the implanted embryos died and were absorbed back into the rats' bodies.

  • Scientists are trying to figure out what exactly it is about microgravity that messes with

  • blastocysts and their ability to implant and grow, but they do have ideas.

  • Like, embryonic stem cells are part of the equation.

  • These are the cells in the blastocyst that differentiate, or diversify into all of the

  • different kinds of tissues in the fetus.

  • Microgravity appears to make them more resistant to differentiating into those more mature cells.

  • It's possible that microgravity interferes with DNA methylation, a process known to affect

  • cell differentiation.

  • Or there could be other factorslike how microgravity messes with the behavior of fluids,

  • and how cells float in fluids.

  • So, at this point, it's up in the air whether space pregnancy is feasible, outside of inventing

  • prolonged artificial gravity.

  • That said, even if we did figure that part out, there's evidence that a fetus couldn't

  • develop in a healthy way in space.

  • After all, gravity isn't only important for the earliest stages of pregnancy.

  • Scientists are pretty sure that it's also important in the third trimester,

  • when it helps the fetus develop its muscles, including in the heart.

  • Gravity may even play key roles in the development of synapses in the brain and sensory tissue

  • in the inner ear.

  • And based on evidence from pregnant mice, it seems like microgravity during orbital

  • spaceflight affects the development of vestibular functionsbasically the sense of balance

  • and motion.

  • So, not great news.

  • And even if we can compensate for microgravity, developing radiation shielding technology

  • strong enough to protect a fetus is a whole other matter.

  • Outside of Earth's magnetic field, the effects of solar radiation are a lot stronger.

  • And we've learned that the developing brain is extremely sensitive to radiation exposure,

  • which can cause DNA damage, brain defects, and increased incidence of cancer.

  • So, while there's a lot we still don't know about how this all works, and while we'll

  • need many more studies in mammals, one thing's for sure: We may get there someday, but there

  • are a lot of small steps to come before humanity can make the giant leap to pregnancy in space.

  • If you like deep dives into incredibly specific questions like this one, and absurdly competitive

  • trivia, and also science poetry, then boy do we have a podcast for you.

  • It's SciShow Tangents!

  • Produced by Complexly and WNYC Studios, it's made by the same people who bring you

  • SciShow!

  • Well, some of them.

  • Lately, they've been recording from home in the name of social distancing, which has

  • involved host Ceri building a blanket fort.

  • Geez, who doesn't have a fully equipped podcast studio in their home already?

  • Get with the program!

  • Check it out at the link in the description -- and thanks for watching

  • {♫Outro♫}

{♫Intro♫}

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B2 中高級

你能在太空中懷孕嗎? (Could You Get Pregnant in Space?)

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    林宜悉 發佈於 2021 年 01 月 14 日
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