I think this question is a joke, but no. Signing a birth certificate doesn't make you responsible for anything. If you separated and she filed for child support, you would be forced to take a paternity test.
A few arguments you could throw out there...
-Should tax payers be forced to pay for other people's mistakes?
-Why is it the publics responsibility? (is it a private matter rather than a public problem)
-What about married teens who choose to have children young?
-Can we prove that more money...