Why can fetus' lay head down without suffering from blood pooling in the brain?

[revpat55]

Another 3am question - you know, the ones that wakes you up at ungodly hours! Does anyone know why a baby in the womb can lay in an upside down position for several weeks prior to birth without any ill effects from blood pooling in the cranial cavity, yet it only takes a few minutes for a human to become unconcious in the same position as the blood is not pumped round the body? I know the oxygen supply is not compromised in a fetus, but the baby's heart pumps its own blood. I guess the answer will be simple & I will look like an idion, but hey!!

[redcrx]

i think their heartbeat is so fast that they dont get effected i the same way that we do.
Plus they turn slowly so they probably have time to get used to it

[wildwood]

The blood pressure only gets up to full power when the fetus takes its first breath.