Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: neilep on 13/06/2008 23:22:44
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Dear Babies and Peeps Who Used To B Babies [::)]
See this sprog ?
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Cool eh ?...it's desperate to come out !
Soon it will turn like this ready to exit !!
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Why not just grow like that in mummys tummy in the first place ?
Do ALL animal babies (born like us) turn like this ?
ewe see..I just don't know...I wish I did !!..Oh my it would my Friday night just so perfect !
.....give me a perfect Fiday night will ya ?
Hugs and shmishes
neil
baby womb orientation enquirer
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Hi Neil
good question!
Contrary to popular belief there's no magic mechanism for turning a baby around as it approaches full term so that it points head-first towards the exit! In fact it's all a question of space. The shape of the uterus naturally positions the baby head first down because that's the position in which it fits best. The random movements of the baby mean that it eventually ends up in this position and, on account of its size, it eventually stays there!
That's not to say that babies can't present the other way around too; certain conditions like fibroids can take up space in the uterus and increase the risk of malpresentation (as it's known), but the vast majority of babies do end up the right way round, which is upside down!
Chris
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What about the weight of the brain and gravity.. wouldn't the head naturally drop down being the heavier part of the baby??
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I'm less convinced of that really, Karen, because the baby is bobbing about in amniotic fluid, so it's not really an issue.
Chris
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It may be more of an issue than you think Chris. The head of a baby grows very rapidly and the skull and neck vertibrae along with the shoulders would be denser than the lower body and eventually tilt the baby providing there is sufficient room to do so and providing the mother is aware of her relationship with the direction of gravity and her posture.
Yet another thought provoking question from Neil.
I believe that gravity plays a massive part in the development of the baby. Take a chick egg for instance. No rotation of the egg = no chick. So does gravity influence the primary circulation that develops long before the heart forms? I am convinced it does. and attribute this to the way solutes migrate through the albumen and carve out a circulation route that drives the whole process in the developing embryo. Ironically the primitive streak resembles my own tubular experiments in miniature.
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If the bird egg is not rotated, the developing embryo sticks to one side of the shell.
Andrew, I would imagine that the effects of egg rotation on embryo circulation are fairly insignificant, as the cardiovascular system already becomes established by the 3rd day of incubation.
http://www.msstate.edu/dept/poultry/avianemb.htm#stages
I think it is wrong to be "convinced" of anything in the absence of sufficient supporting evidence.
Chris, how does the human fetus deal with the increased blood flow to the brain in the late stages of gestation, due to the head-down position? Isn't this bad for the brain?
Conversely, could the position actually enhance brain development?
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hi Stefan
that's a good thought, but flawed for the following reason. Human foetal mean arterial blood pressure is about 60mmHg. The hydrostatic difference between a head up and head down position - in other words how much extra pressure is added by lowering the head will be about 60-100 mm of WATER (because blood is effectively water); therefore arterial perfusion pressure is not significantly affected by the position of the head. Compare this with a giraffe, however, where the extremely long neck adds thousands of millimetres of water pressure and you're talking a different story entirely.
The other point to bear in mind with a human baby is that the mother is often recumbent (lying down) and hence a developing foetus could not always rely on this gravity assist effect. If it were therefore this critical to neurological perfusion then women who are on their feet more should have brainier babies, whilst women who give birth to breech (feet-first) babies should have less cerebral children. This doesn't seem to be the case and although breech delivery is associated with more problems around the time of delivery, in the long term there is no developmental or health impact; at least as far as I am aware.
Therefore, I stick to my original conclusion that the foetus takes up the most space-efficient position, which later in pregnancy in a normal uterus means head first downwards.
Chris
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Hi Chris. Good points. However, due to the baby being suspended in fluid, baby will always be re-adjusting posture in relation to mums own posture and the angle of the body might not be as horizontal when mum is sleeping as one would expect. Furthermore, mum is always trying to get comfortable in bed and changes posture from side to back and to side giving some of the rotations of the developing baby. Again sitting, standing and walking will change the direction of gravity and yoga is found to be very helpful for an expecting mother.
RE Giraffe: You may be interested in reading an article I posted in another thread relating to Giraffe blood pressure standing and laying flat. Ironically, the BP rises when the animal is flat and reduces when the animal is standing.
hi Stefan
that's a good thought, but flawed for the following reason. Human foetal mean arterial blood pressure is about 60mmHg. The hydrostatic difference between a head up and head down position - in other words how much extra pressure is added by lowering the head will be about 60-100 mm of WATER (because blood is effectively water); therefore arterial perfusion pressure is not significantly affected by the position of the head. Compare this with a giraffe, however, where the extremely long neck adds thousands of millimetres of water pressure and you're talking a different story entirely.
The other point to bear in mind with a human baby is that the mother is often recumbent (lying down) and hence a developing foetus could not always rely on this gravity assist effect. If it were therefore this critical to neurological perfusion then women who are on their feet more should have brainier babies, whilst women who give birth to breech (feet-first) babies should have less cerebral children. This doesn't seem to be the case and although breech delivery is associated with more problems around the time of delivery, in the long term there is no developmental or health impact; at least as far as I am aware.
Therefore, I stick to my original conclusion that the foetus takes up the most space-efficient position, which later in pregnancy in a normal uterus means head first downwards.
Chris
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Thanks Chris for clearing that up :)
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For the same reason that sleeping upside down (trendelenburg) causes degeneration and rapid muscular atrophy, heart atrophy, decalcification of the bones, kidney, liver, gall and bladder stones, respiratory and neurological dysfunction. And increased levels of toxins due to impaired renal function might tell us something about why baby develops the right way up perhaps?
I was expecting a lot of replies and interest to this thread it is a valid observation that babies develop in alignment with gravity and turn to exit the womb at birth.