Dier v. Peters (Iowa June 1, 2012) offers a good discussion of the debate about paternity fraud lawsuits, including citations to cases that reject such a cause of action and to cases that accept it.
This particular case concludes that, if a woman fraudulently tells a man that he was the father of her child, and the man voluntarily pays child support (not pursuant to a court order), he is entitled to a return of the payments. This seems right to me, on basic principles of the law of fraud; what to do about past court-ordered payments is a more complicated matter, having to do with the proper means of reversing existing judgments, though I think some such remedy should be available there as well. In any case, it’s an interesting opinion, with an interesting concurrence.