Most women give birth lying down - and that's nothing to do with biology or medicine.
In fact, the real reason is actually a little creepy and it's all to do with one man's very weird fetish.
Back in the 17th century, King Louis XIV of France was obsessed with seeing his children being born.
"Prior to this time, the recorded history of birthing indicates upright birth postures were used extensively," Professor Lauren Dundes writes in the American Journal of Public Health.
There was nothing wrong with the common birthing practices from that for one thing: the king didn't have as good a view of the "action" as he liked to have, if his wives and mistresses were giving birth in an upright position.
According to the American Journal of Public Health, the reclining childbirth position is all his fault and, as such, a relatively new way of giving birth (he ruled between 1643 and 1715).
King Louis XIV fathered 22 children and changed the way women give birth because he wanted a better view of his children being born.
"Since Louis XIV reportedly enjoyed watching women giving birth, he became frustrated by the obscured view of birth when it occurred on birthing stool, and promoted the new reclining position," the journal states.
His weird fetish meant that women began lying on "birthing tables" with their feet in stirrups and, in the case of the birth of his children, he'd be peeping behind a screen to watch the action unfold.
Once the lower classes found out his method, it began to spread.
"The influence of the King's policy is unknown, although the behavior of royalty must have affected the populace to some degree. Louis XIV's purported demand for change did coincide with the changing of the position and may well have been a contributing influence."
Some experts claim the reclining birthing position, still the most common position used today, can prolong labour and even increase the need for a C-section.
The natural birthing position is actually squatting, kneeling or going on all fours - positions that make a woman push the baby out with a little help from gravity.
X-rays have shown that giving birth squatting, kneeling or on your hands and knees mean the pelvic outlet becomes wider, making labour shorter and easier.