It is a matter of you play, you pay. That's more or less the rule that society has set and there are no exceptions that I know of.
In other words, if there is a kid, and you're the father, you're responsible, regardless of any decision or action on the part of the mother.
Edit Add: Please understand that the law may view the matter differently. Those are my opinions and if I had a say in the matter, that is how I would view the responsibility.
However, ymmv (Your mileage may vary), which means that it really is a matter of how the laws are written and enforced in the appropriate jurisdictions.