Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: evan_au on 12/07/2013 14:46:17
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I am approaching the end of my third trimester. The baby has got itself at long last in the right position.
An unborn baby's head lies downwards for the birth, and can remain like that for many, many weeks.
If I hung upside down for weeks, all my blood would be swimming around my brain, and I will be a bit dead. So how come an unborn baby is OK?
How does a baby withstand a prolonged headstand in the womb?
What do you think? Answer in the show next week.
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The blood pressure experienced in the head during a headstand is caused by the difference in height between the lowest and highest points.
This has more impact on adults than a baby because:
- An adult human is much larger than a baby in the womb, and so potentially exposed to greater pressures
- The baby is curled into a tight ball, so the pressure differences are less.
- Human adults have spent much of their lives feet-down, so the veins and arteries in our legs have been exercised to withstand this increased pressure. But most adults do not regularly do headstands for long periods, and the blood vessels would find this an unaccustomed pressure, perhaps resulting in a nosebleed (or the equivalent hemorrhage inside the skull, which is much more severe).
- A human trying to do a headstand would be doing it in air, while the baby lies in amniotic fluid, which provides a counterbalancing external pressure which is greater at the lowest end, counteracting the tendency towards nosebleed.
To see what the baby experiences, try doing a headstand in a swimming pool - but staying down for a couple of weeks is not recommended.