There is no question that he should be able to. For the mother to be able to carry the baby to term and then force money out of him is no less a violation of his rights than forcing the mother to carry the baby to term a violation of her rights.
Why? Pregnancy is a known consequence of sex. It doesn't happen all the time, and it can be prevented in most cases, but it's a known consequence nonetheless. We prosecute people for felonies if they drive drunk and kill someone, though there's absolutely no INTENT to kill anyone ever demonstrated. If people can only be held responsible for intended actions, you're saying the concept of negligence should not exist.