system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can babies spend weeks head down in the womb, but it becomes dangerous to hold them upside-down for longer than a few moments once they are born?
gpt
I asked the doctor about this. In the womb, the amniotic fluid supports the whole body. When the baby is upside down, it's never been right side up. it's heart is used to no direction. when the body has been out for a while, there is no support by the fluid, and the heart rapidly becomes used to prone and upright.