Hmmm... will have to think this through. I was a teen parent (just turned 18). The bad parenting, I guess, was having a child who felt she had to flee her home at 16 just to be safe and then (not consciously understanding) hooked up with a man much older than her (think father figure).
That being said, I know of several people who come from good homes with loving and kind parents, and yet ended up an unwed teenage mother.