I'd like to have a community of humans live indefinitely in space habitats (think space stations supporting mining operations in the asteroid belt).

The technology would be "day after tomorrow"-level; no anti-gravity, no effector fields, or the like.

So, my problem is that I'd like to have happy space families, but I've read that long-term zero-G living is dangerous and bad for many physical systems, especially bones. The big question is whether a child can successfully be brought to term in zero gravity.

Will the children be able to be born? As a possible mitigation, we could spin the habitats, but I'm not sure if that will be "good enough" to substitute for gravity, nor whether current construction methods will be able to hold up under relentless spinning.

Please help, the gallant colonists of Alpha Colony need answers!

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    $\begingroup$ Food for thought: will they prefer natural delivery or C section? $\endgroup$
    – user6760
    Commented Nov 6, 2017 at 4:27
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    $\begingroup$ we could spin the habitats, but I'm not sure if that will be "good enough" to substitute for gravity - there is no physical difference between living under 1g gravity and living in a spinning ship which replicates 1g gravity. In other words there is nothing special about gravity as a force. $\endgroup$
    – bon
    Commented Nov 6, 2017 at 10:19
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    $\begingroup$ Technically there is a difference, but it's not important for everyday life. $\endgroup$ Commented Nov 6, 2017 at 10:21
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    $\begingroup$ “Day after tomorrow.” Alright guys, we have two days to build those anti-gravity and effector fields. No pressure. $\endgroup$
    – DonielF
    Commented Nov 6, 2017 at 16:13
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    $\begingroup$ @DonielF not "no pressure" guys, "no gravity"! See, this is why the project is behind schedule... $\endgroup$
    – akaioi
    Commented Nov 6, 2017 at 16:28

5 Answers 5


Last time I looked into this I was amazed these experiments (mammalian conception to delivery in orbit) had not been done. I figured I just had not found it and so I dug in this time. For mammals, they have not been done. Pregnant rats have gone to space and come home and delivered so microgravity is not immediately lethal to a fetus. Rats mated in space (no pregnancies). Rat pups nursed in space (it is tricky for them to orient; I think humans will have less trouble with that). The news from 2017: freeze dried mouse sperm (I did not know that was possible - the freeze drying) can come home and make babies. From that article.

Sayaka Wakayamaa et al, Healthy offspring from freeze-dried mouse spermatozoa held on the International Space Station for 9 months. PNAS 114(23)5988–5993

So far, the effects of microgravity on early development have been studied using sea urchins, fish, amphibians, and birds. These studies have concluded that microgravity does not prevent animal reproduction. However, because of the difficulty in maintaining mammals and performing experiments in space, studies of mammal reproduction in space have not progressed as well as in other animals, and only a few papers have been published. Those studies and our previous study have suggested that mammalian reproduction in space under conditions of microgravity cannot be easily compared with reproduction in other species.

It is lame to answer a question with "no-one knows" but for the prospects of full on start to finish mammalian pregnancy and gestation in space I think no-one knows. It is a surprise to me that is still the case.

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    $\begingroup$ +1 for a no one knows answer. Sometimes pointing out the boundaries of what is known is enough to justify the funds to get research done. $\endgroup$
    – steverino
    Commented Nov 6, 2017 at 4:09
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    $\begingroup$ note the study was focused on the effects of radiation on fertilization not microgravity and development. Studies focusing on the gravity do not show promising results, the pre-implantation stage of embryo development is believed to be the most vulnerable. journals.plos.org/plosone/article?id=10.1371/… of course microgravity plays havoc on adults too (like making them go blind) it just takes longer, so simulating gravity will be important no matter what. $\endgroup$
    – John
    Commented Nov 6, 2017 at 5:33
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    $\begingroup$ +1 for letting me know astronauts in space are milking male rats and freeze dry the results. Tax money well spent $\endgroup$
    – Raditz_35
    Commented Nov 6, 2017 at 8:50
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    $\begingroup$ @Raditz_35: ...for the purpose of researching the effect of higher radiation on the sperm DNA. Yes, that is tax money well spent, and it's not as if it were a major cost factor. Better than many wasteful projects conducted here on earth. Are you sure you aren't just put off by the perceived grossness of "milking" rats? $\endgroup$
    – DevSolar
    Commented Nov 6, 2017 at 9:38
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    $\begingroup$ "Rats mated in space (no pregnancies)". If that turned out to be due to lack of gravity messing with sperm travel (or any other space reason), you could make a good story or plot point out of couples deciding to have a child needing to return to the planet. It's a cool way of adding artificial natal philopatry to humankind, and what that could mean by way of control by a government/family body or wrapping the act into some sort of religious event. $\endgroup$
    – Philbo
    Commented Nov 6, 2017 at 10:40

Will the children be able to be born?

For all we know: Yes.

I shamelessly copy from two comments below the question by user6760 and bon.

For the birth gravitation is usually helpful in assisting the pushing force of the contractions. Many women stand or sit during the birth. However, it is conceivable that even without gravitation there is enough force to push the baby out of the uterus. In the same way one could also help and create artificial pull by applying a suction cup to the head of the baby and pull.

Or one could apply a C-section which would eliminate the need for gravitation at all during birth.

Rotating elements creating artificial gravitation similar to our gravitation level are feasible. During infinite space travel you don't have to do without gravitation. In the absence of friction with the surrounding space, such a rotation could be maintained very efficiently. Centrifugal forces are exactly the same as gravitational forces. Regarding the endurance of the construction towards rotation, please note that space vehicles have to endure a multiple of that force during launch and they do. An infinitely traveling human space race surely would replace weak parts over time with newer parts to hold it all together.

And even if for most of the time you would life in low-G environments, by doing sports in this environment (pushing against each other, ...) one could keep the muscles trained.

For the skeleton it may indeed by bad in the long run. We don't have reliable long term information about that. The human race living in low-G might indeed evolve different (less upright). Maybe modern medicine (the technology of today to tomorrow) could strengthen the bones artificially (increased calcium uptake,...).

  • $\begingroup$ Or one could apply a C-section which would eliminate the need for gravitation at all during birth - oh, but the mess... $\endgroup$ Commented Nov 6, 2017 at 18:07
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    $\begingroup$ "water birth" is a thing for contemporary humans on Earth, and my wife enjoyed the relief of swimming while very pregnant... low gravity is probably more comfortable for both mom and baby than normal gravity during pregnancy and birth. $\endgroup$
    – Nathan
    Commented Nov 6, 2017 at 19:41
  • $\begingroup$ Trilarion, very interesting angle here. I wonder if the women would go into the center of the habitat (low/zero-g section) for giving birth. The exercises you're speaking of, those are "isometric exercise", yes? $\endgroup$
    – akaioi
    Commented Nov 7, 2017 at 4:23
  • $\begingroup$ @Nathan water does not remove gravity at all. It just sustain your body. $\endgroup$
    – Antzi
    Commented Nov 8, 2017 at 2:52
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    $\begingroup$ water birth is just interesting to compare since buoyancy is often used to simulate low gravity $\endgroup$
    – Nathan
    Commented Nov 10, 2017 at 22:11

Ugh... So, yeah, it's never been done - if it had, this would be open and shut.


  1. Human women often give birth prone such that the force of gravity is perpendicular to the direction they're pushing the baby. Therefore, there's no reason to assume that [most] women aren't strong enough to give birth in zero-g.

  2. Women from a variety of species (including some humans) give birth under water where the forces of buoyancy and gravity are equal and opposite, so there's still no reason to suspect that gravity is a requirement for birth.

  3. One of the long term effects of weightlessness is that our bones become weaker. It's possible (though, highly unlikely because the baby doesn't go between hips - it goes through cartilage and other tissues) that this would mean that giving birth necessitated a risk of breaking one's hips. It's also possible that the bones could become more pliable, either because of the sometime inverse relationship between strength and plasticity, or because of a drug/supplement administered during gestation.

  4. If birth without undue risk of catastrophic injury was not possible, there's always Cesarean section, see bulldogs.


In the weeks to hours before birth, the baby resides lower in the abdomen - a transition that physicians call "lightening". A hypothesis has been advanced that a baby won't drop without gravity. On the surface, it seems to have merit, but babies drop while expecting mothers are in a variety of positions. In addition, dolphins appear to have a similar phase, so at the very least, mammal babies can drop without gravity. Earth women have exercises and movements which hypothetically move the baby into position, but while that research appears to be in its infancy, there's no reason to avoid talking about the zero-g versions of the same exercises.


Humans carry babies in their wombs surrounded by hydro-static pressure. Since Earth women do yoga, swim and sleep, it's pretty clear that their orientation does not effect their ability to bring a baby to term. For women to need gravity to bring babies to term would require proof.


Again, nobody wants to admit to having had sex in space, but humans are endlessly creative when it comes to this. I will not be adding a link.


Nature will find a way. There are few things that cause rapid evolution in "natural" species, but illnesses and breeding problems are at the top of that list. Nature is neither fair, nor kind about this, so there would be some cruel generations where natural selection takes care of this problem. That could have it's own consequences because our powerful brains are related to the long gestation times. The other option would be to guide evolution with Genetic Engineering, but that tech is probably a long way away.


If you want it to be an issue, you can, but I wouldn't bat an eye if a fiction writer told me that zero-g birth was commonplace and about as catastrophic as Earth birth.

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    $\begingroup$ "Humans carry babies in their wombs surrounded by hydro-static pressure" that's a really good point which I hadn't considered. The issue I'm worried about is at the very end, when the baby "descends" to get into position ... might want some gravity for that. As other posters have said, C-section might be the preferred option here. Your comments have mitigated a lot (not quite all!) but a lot of my concern! $\endgroup$
    – akaioi
    Commented Nov 7, 2017 at 20:22
  • $\begingroup$ "laying down" -> "lying down". Please. $\endgroup$
    – ErikE
    Commented Nov 7, 2017 at 23:16
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    $\begingroup$ Babies and children need quite some "exercise" to grow up really healthy, but from our experience with individuals with certain permanent disabilites (or ones growing up in front of a TV), we know this is not fatal, and could most likely be taken care of by some daily age-adapted gynmastics also in space. $\endgroup$
    – Karl
    Commented Jan 2, 2018 at 21:00

Having done it myself, I know that birth is a very traumatic experience, for all persons involved. Pregnancy can also be very unpleasant.

There will be no room for people on space stations who are going to be sick and wobbly and faint for months at a time.

Your future humans will leave gestation to a nice safe, warm automatic womb, providing everything the baby colonist needs, including gravity, and when it's finished growing, you open the lid and get it out.

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    $\begingroup$ Nice for near future or beyond, but right now we don't have the tech to grow a baby in a machine. $\endgroup$
    – JPhi1618
    Commented Nov 7, 2017 at 16:22
  • $\begingroup$ @JPhi1618 I'm pretty sure we can have that kind of tech in a decade or so, if we just allow cloning humans. $\endgroup$
    – Clearer
    Commented Jan 2, 2018 at 23:10
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    $\begingroup$ The space program has had no shortage of encounters with vomit, urine, and stray pieces of feces floating around the cabin. But there's still a risk that when the water breaks, the ship's systems will have met their match. It's also said to be possible to drown in a quite small amount of water in zero G if it gets stuck in the throat. Birth may indeed be a traumatic experience for all involved... $\endgroup$ Commented Jun 16, 2022 at 14:26

My suspicion would be that it is possible to make babies is space, but I think there would be a far higher rate of in-utero fetal demise. Microgravity shouldn't cause any obvious issues with conception, formation of a blastocyst, or implantation (emphasis on the obvious). The placenta forms in any orientation so that shouldn't be an issue. For the first 32 weeks or so of a pregnancy baby spins and flips like a toddler in a bouncy house, so orientation doesn't seem to be particularly important. Some of the other comments suggest that gravity plays a role in fetal engagement with the cervix, descent, and birth, but at the end of the day those are mechanical problems that can be solved. We deliver babies all the time without Mom going into labor either through induction of labor or via cesarean.

Where you may get into trouble is with Vircohow's Triad, particularly the stasis corner. An astronaut recently had a blood clot form in his neck while in microgravity, possibly due to an increase in blood pooling in the head and neck in microgravity (gravity usually "pulls" the blood back to the heart from the head). The placenta has a boatload of blood vessels for nutrient exchange with baby and can cause fetal demise if a clot forms in it. It's unclear whether microgravity would increase susceptibility to blood pooling in the vessels in the placenta, but if it did that could increase the rate of fetal death.

I think the nastiest thing about growing up in microgravity would be changes in the vestibular system of your inner ear that helps you balance. A child's brain raised in microgravity would never receive the typical signals from the inner ear that you or I get while being accelerated into earth's surface. This would either lead to something like ambliopia of the ear, where the brain simply ignores the signals it gets, or re-interpretation of the signals as they operate in microgravity (more likely). The second would cause people born in space to be very disoriented at mild to moderate linear acceleration (such as spacecraft maneuvers) the same way we get disoriented on a merry go round. This same effect would happen when they go down a gravity well, though presumably they would eventually get used to it the same way astronauts get used to the vestibular changes in microgravity. Those first couple days would be nasty though.


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