Funny, I never even thought about that. I guess it would happen if your cycles came back and were super regular. I've been due all over the month (the 11th, the 4th, and the 24th) and have given birth with an okay variety (20th, 16th, and 9th). But my mom had all of us in the "teens" (12, 16, 18). And I know a lot of people who have that same thing with their kids.