# Is the skin/placenta thin enough to allow any light into the human womb during pregnancy? **URL:** \ **Category:** Factual Questions\ **Created:** [February 18, 2017, 3:46pm UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148 "2017-02-18T15:46:41Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Waxwinged](https://avatars.discourse-cdn.com/v4/letter/w/c2a13f/32.png) [@Waxwinged](https://boards.straightdope.com/u/Waxwinged)\ **Post date:** [February 18, 2017, 3:46pm UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/1 "2017-02-18T15:46:41Z")
Just curious as to whether or not the fetus is in complete blackout during the entire thing. ---
**Author:** ![Dr\_Paprika](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr_paprika/32/3042_2.png) [@Dr\_Paprika](https://boards.straightdope.com/u/Dr_Paprika)\ **Post date:** [February 18, 2017, 3:53pm UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/2 "2017-02-18T15:53:31Z")
It may be able to let light in due to its structure. But it is generally full of blood to nourish the growing fetus. And it is not usually located in a solarium. I often see fetuses wave or turn when doing ultrasounds, though, so maybe you’re on to something. ---
**Author:** ![Nametag](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nametag/32/406_2.png) [@Nametag](https://boards.straightdope.com/u/Nametag)\ **Post date:** [February 18, 2017, 6:13pm UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/3 "2017-02-18T18:13:15Z")
Neither the skin nor the placenta matters - the uterine wall is thick enough. ---
**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\ **Post date:** [February 18, 2017, 7:44pm UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/4 "2017-02-18T19:44:50Z")
This is why they sell The Little Placenta Light - so the kid will be able to read during the long months of gestation. ---
**Author:** ![Waxwinged](https://avatars.discourse-cdn.com/v4/letter/w/c2a13f/32.png) [@Waxwinged](https://boards.straightdope.com/u/Waxwinged)\ **Post date:** [February 18, 2017, 10:32pm UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/5 "2017-02-18T22:32:53Z")
> [@Dr\_Paprika](#): > > It may be able to let light in due to its structure. But it is generally full of blood to nourish the growing fetus. And it is not usually located in a solarium. > > I often see fetuses wave or turn when doing ultrasounds, though, so maybe you’re on to something. … Okay, I expected better from the Straight dope. Amniotic fluid that surrounds the fetus is clear/yellowish. Ultrasounds could be showing regular movements, or fetus could be reacting to slight pressure as well. ---
**Author:** ![Spit](https://avatars.discourse-cdn.com/v4/letter/s/76d3ee/32.png) [@Spit](https://boards.straightdope.com/u/Spit)\ **Post date:** [February 18, 2017, 11:16pm UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/6 "2017-02-18T23:16:08Z")
I would shine my handheld spotlight on my wife’s stomach during the 9th month, and all three of our kids would start kicking. They were definitely getting some kind of glow or something in there. I also used to talk really loudly, “Hey! What’s going on in there?” and that would cause some movement. ---
**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\ **Post date:** [February 18, 2017, 11:51pm UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/7 "2017-02-18T23:51:59Z")
> [@Spit](#): > > I would shine my handheld spotlight on my wife’s stomach during the 9th month, and all three of our kids would start kicking. They were definitely getting some kind of glow or something in there. I also used to talk really loudly, “Hey! What’s going on in there?” and that would cause some movement. Maybe artificial induction of labor could be replaced by having cops yell “Get down on the ground!”. :dubious: ---
**Author:** ![Weisshund](https://avatars.discourse-cdn.com/v4/letter/w/ba8739/32.png) [@Weisshund](https://boards.straightdope.com/u/Weisshund)\ **Post date:** [February 19, 2017, 1:00am UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/8 "2017-02-19T01:00:15Z")
> [@Waxwinged](#): > > Just curious as to whether or not the fetus is in complete blackout during the entire thing. Aside from stucking a Q-beam to the womans stomach, which might show as a red glow inside, you are not getting normal light past 7 layers of skin, fat, muscle, uterus, fluid, placenta etc. it’s quite dark in there. As far as reacting to an ultrasound, you got a kid, sitting in fluid, fluid thats all the way into it’s ears touching its eardrum. Ultrasound is, well sound. So it could very well be that the kid can kind of hear it or something. I doubt they could see any disturbance in the fluid, because A) its dark as hell B) they dont exactly focus their eyes very well when they are born, hard to practice that when it’s dark as hell. ---
**Author:** ![Dr\_Paprika](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr_paprika/32/3042_2.png) [@Dr\_Paprika](https://boards.straightdope.com/u/Dr_Paprika)\ **Post date:** [February 19, 2017, 2:51am UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/9 "2017-02-19T02:51:18Z")
The placenta is a thin structure. The uterus is thick and muscular. The placenta contains the blood supply. I like the idea of a bright womb but would guess before delivery it is tough to make out the words while writing letters. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [February 19, 2017, 3:16am UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/10 "2017-02-19T03:16:25Z")
It’s several a layers of skin and muscle. Take one of the super high powered LED flashlights that are all over the place these days and put it in your mouth and shine it through your cheek. You can usually see just a little bit of light coming through the skin wall. Now try shining it through your palm which is analogous to all the layers you would have to go through to get to a baby. The answer is no. It’s pitch dark. ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [February 19, 2017, 5:18am UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/11 "2017-02-19T05:18:43Z")
Wouldn’t it depend on how bright the light is? I mean, my LED desk lamp is visible through my palm as a reddish glow. (It also apparently goes through whatever tissue is between the roof of my mouth and my eyes, because when I put it in my mouth, it becomes visible as a bizarre red background glow that appears brightest in the outside upper corners of my vision.) ---
**Author:** ![race\_to\_the\_bottom](https://avatars.discourse-cdn.com/v4/letter/r/c4cdca/32.png) [@race\_to\_the\_bottom](https://boards.straightdope.com/u/race_to_the_bottom)\ **Post date:** [February 19, 2017, 8:45pm UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/12 "2017-02-19T20:45:58Z")
I suspect that light does not affect fetal development, but it has been proven that babies hear a lot and are affected by it. They start to learn language and develop a preference for the diet of the mother as well. You can Google all this stuff. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [February 19, 2017, 11:00pm UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/13 "2017-02-19T23:00:51Z")
> [@chorpler](#): > > Wouldn’t it depend on how bright the light is? It would have to be very bright; the [eyes of infants](https://en.wikipedia.org/wiki/Infant_visual_development) are much worse at seeing in dim light than an adult’s. > [@](#): > > The threshold for light sensitivity is much higher in infants compared to adults. From birth, the pupils of an infant remain constricted to limit the amount of entering light. In regards to pupil dimensions, newborn’s pupil grow from approximately 2.2 mm to an adult length of 3.3 mm.[2] A one-month-old infant can detect light thresholds only when it is approximately 50 times greater than that of an adult. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [February 20, 2017, 9:13am UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/14 "2017-02-20T09:13:40Z")
> [@Weisshund](#): > > … > As far as reacting to an ultrasound, you got a kid, sitting in fluid, fluid thats all the way into it’s ears touching its eardrum. > Ultrasound is, well sound. > So it could very well be that the kid can kind of hear it or something. > … No way. Ultrasound scans are above 10 **MHz.** Human’s can hear no higher than around 20 **kHz.** Not even close. Besides, the definition of ultrasound is sound waves beyond human hearing. ---
**Author:** ![kayaker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayaker/32/441_2.png) [@kayaker](https://boards.straightdope.com/u/kayaker)\ **Post date:** [February 20, 2017, 12:28pm UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/15 "2017-02-20T12:28:47Z")
All y’all talking about shining a bright light into a woman’s stomach realize the babee is in her uterus, which is in her abdomen, right? Her stomach contains things like linguini with clam sauce and chef salad. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [February 20, 2017, 2:03pm UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/16 "2017-02-20T14:03:53Z")
> [@astro](#): > > Now try shining it through your palm which is analogous to all the layers you would have to go through to get to a baby. I tried this in a dark room, and, though dim, you can definitely see some light through my palm. ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [February 20, 2017, 2:21pm UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/17 "2017-02-20T14:21:13Z")
My wife is pregnant and she is going to the beach ? Is there a sunscreen she can put on the fetus ? (He said humously … hopefully… ) No need. While the blood vessels in your finger can let a glow flow seemingly “through” the finger, the various layers, of different densities , of materials in the structures of the abdomen will make it quite dark in there. A suitable non-burning (cold) light source is required for keyhole surgery… they can’t just stick an incandescent bulb inside someones body… and they need it quite bright as the light source will get covered in blood… So they use a fibre optic to send just the light down into the body and have the heat outside. So I am sure that the fetus does not “see” until born. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [February 20, 2017, 2:27pm UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/18 "2017-02-20T14:27:27Z")
The amount of flesh between the outside world and the foetus - especially in late pregnancy - is not all that great. Indeed one in three mothers will experience some level of Diastasis Recti - a separation of the muscles of the abdominal wall - leading to even less flesh in the path. I have no trouble believing that a foetus will find itself in a world of dim light at times. ---
**Author:** ![Mrdeals](https://avatars.discourse-cdn.com/v4/letter/m/ea666f/32.png) [@Mrdeals](https://boards.straightdope.com/u/Mrdeals)\ **Post date:** [February 20, 2017, 5:19pm UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/19 "2017-02-20T17:19:16Z")
> [@Francis\_Vaughan](#): > > The amount of flesh between the outside world and the foetus - especially in late pregnancy - is not all that great. Indeed one in three mothers will experience some level of Diastasis Recti - a separation of the muscles of the abdominal wall - leading to even less flesh in the path. > > I have no trouble believing that a foetus will find itself in a world of dim light at times. I came here to mention this too. I have a medical book which depicts (i’m sure very rare) incidents of the baby punching right through the mothers uterus and stomach area. Around the last couple weeks of pregnancy all tissues involved are very thin. ---
**Author:** ![Blue\_Blistering\_Barnacle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blue_blistering_barnacle/32/3386_2.png) [@Blue\_Blistering\_Barnacle](https://boards.straightdope.com/u/Blue_Blistering_Barnacle)\ **Post date:** [February 20, 2017, 10:07pm UTC](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148/20 "2017-02-20T22:07:25Z")
In late term, the uterine wall is quite thin, especially in some expectant mothers. I have read (not recently at all) that enough light can penetrate the scalp and skull to faintly illuminate the pineal gland. This is difficult to credit, but if light can get there, then yes, I could believe it could get to a fetus. Even if not as sensitive to dim light as us, they must be pretty well dark adjusted! Lastly, when I was a kid we would shine regular flashlights through our hands to see the creepy dim red glow all the time. Doctors used to use transillumination all the time, eg for sinus disease. [Next page](https://boards.straightdope.com/t/is-the-skin-placenta-thin-enough-to-allow-any-light-into-the-human-womb-during-pregnancy/780148.md?page=2)