My 1st experience with birth was when I was 4 years old, and my first sister was soon to be born. This was in the Fall of 1964, or early January 1965.
While I don't remember it, my Mother had a story she always delighted in sharing.
It seems that she always wore dresses with zippers down the front, and one day I asked about her big belly, and she said she was carrying a baby, and when the time came she would go to the hospital so Dr.Weston could take it out of her.
Well, genius that I was, even at that tender age, I knew something that seemed obvious and, far easier in this regard, than going through the trouble of traveling to the hospital.
I wanted to know why my Mom couldn't just unzip her dress and take the baby out?
Mom never told me how she answered that one, that I recall. :-D
As for when I learned the REAL facts of life, well it had to have been in Junior High School.
I don't remember a specific sit down confab with Mom on the issue, however, just that in 8th grade we had a few sessions in biology class where we even saw a film of child birth.
Several guys fainted, and had to be revived with smelling salts. :-D