If you're not ready to have a kid, you're not ready to have sex, plain and simple. (coming from an almost 19-year-old).
We had a a guest baby in class the other day for observation--cutest thing ever, but the child of young, irresponsible parents who had essentially made this child a Shaken Baby. Brain damage, cerebral palsy, the whole 9 yards.
I'll get off my soap box now.