The youngest pregnancy on record occured in a 5-year-old.
That is just sad.
But apparently it is possible. (Hopefully rare, though.)
I wonder, with girls menstruating earlier and eariler, what is the age we should tell them about it? I wouldn't want it to come as a shock, but a child age 6 or 7 may not fully understand the explanation.
When I was 11 I had a bladder infection where I urinated blood. I thought I had my period because it looked like only blood and not urine. I wore tampons for a few weeks straight (!) and didn't say anything to anyone. I didn't have a working knowledge of menstruation and reproduction until I was 16. It would have been nice to know before then.