There is no way to get teenagers pregnant without a mod. Check your favorite modding site, but be careful as mods affect the way the game works and may cause bugs or other unwanted effects.
If she's under the age of consent (which may vary depending on where you live), you should take every precaution possible to ensure you're not anywhere near her when your...
Press Ctrl-Shift-C and type in "Testingcheats on" (without the "s) and then you can shift click on a Sim or mailbox and stop the needs from going down.
Yes, if you don't use cheats or mods. Only adult male Sims will become pregnant if they're abducted via the telescope. However, the Tombstone of L and D's "Make me...
Make sure you take care of your Sims' needs. Be sure to use an umbrella in the rain, wear light clothing in the summer, warm clothing in the winter, etc.