Weird, a colleague and I were discussing this just today.
A woman can have a "paper abortion;" she can give the baby up for adoption.
A man has absolutely no power in the situation. If he wants to keep the baby but she doesn't want to carry it, too bad. If he wants her to abort but she won't, too bad. That's a consequence of biology, yes, but so what? There is still an inherent and large imbalance there: The woman's decisions completely impact the man's life and the man has no decision making ability at all.
The only real question here is whether or not the current situation meet our standards of ethics, specifically the idea of equality before the law. Our system strives to treat everyone equally and it's pretty clear to me that we don't treat men equally under the law. The only solution is this idea of a paper abortion. Allow men the right to terminate their responsibilities under the same restrictions women are subjected to. But that decision is forever. From that point forward, the man is never allowed to see the kid; it would be as if the fetus was terminated.
The fatal flaw with this is that it totally ignores human nature. What if the couple gets back together? What if later on down the road, the kid wants to meet the dad? What if the dad regrets it and wants to see the kid?
As such, I can't endorse the idea of a paper abortion. Once a kid is born, both parents are responsible. That's just the way it is.