From the Insimenator download page:
"PLEASE NOTE: The InSIMenator does not enable teen pregnancy, in and of itself. The impregnation options MAY or MAY NOT work for teens in your game depending on which other mods (teen woohoo mods) that you are currently using."
http://www.insimenator.org/showthread.php?t=269For successful teen pregnancy, you need a teen wooho mod or else Inteenimator.
See last sticky thread on the WCIF Forum:
http://www.insimenator.org/showthread.php?t=28933for info about where to find that.