I never used a condom when My girlfriend and I were 15-16... For the whole of 2007 and first half of 2008 nothing lol.
We weren't trying for a kid or anything... I was just too lazy to put it on.
I'm 18 now and we have a beautiful 12 month old girl who I'm so glad came into our lives.
Now I know better. 1 child is more than enough. I don't know how Jon and Kate manage lol.