An unplanned and unwanted pregnancy can dramatically affect an otherwise loving long-term relationship. Some men rejoice, but others simply aren't ready to be fathers. If they discussed the possibility and specifics at the start of the relationship, he may hope she's going to stick to the original plan and terminate the pregnancy. And she might -- but for some women, getting pregnant can start clocks ticking and make them suddenly want to be mothers, despite previous agreements.
In either case, the final decision is hers, which means she has ultimate say in whether or not you become a father. This can put tremendous stress on a relationship, particularly if don't want to have a child, but don't want to lose the girl, either. While you can't force her to do your bidding, you can get her to consider your wants and desires if you approach her correctly.
If you've followed all of these steps and your woman decides to have the baby anyway, this does not mean you're required to get married or move in together. You'll probably want to provide for your child regardless, but if you've been clear about your intentions from the start, you are not obligated to contribute beyond what your conscience and the law expects of you. This was her decision, not yours, and the bulk of the responsibility is now hers.
Prenatal pros: Take a moment to spell this out for her when she gives you the final decision; it may just sway her over to your side.