If contriception is used by both parties, but the male is mentally or financially capable of being a father, but the woman chooses to keep the child. Why should the man pay? Or even more sinister, what if he's tricked or lied to in the process? If it is her body and her right to CHOOSE, then it should be her right to choose to pay on her own and take responsiblity for her CHOICE. Instead of heaping it on the male.
I say that, because on the other side of the coin, the man can not force the woman to go to full term and deliver the baby for him to care for. The male has no rights to stop a woman from ending the life of what is his child as well.
Possession being 9/10ths of law, does not make the life inside a woman her sole property.
In the womb, a fetus is not a person. It is a fetus and yes it's sort of owned by the woman. Since she is the one who has to be pregnant, she's the one who has to decide whether or not to abort. It sucks for the guy, but biology doesn't care about equality. This burden of childbearing also sucks for women at times too. Pregnancy complications are not uncommon at all and even low risk, healthy pregnancies can be very difficult physically.
The reason a woman can't just assume total 100% responsibility for a child and let the man off the hook is because the right to child support is the right of the child. A mother can't ethically waive her child's rights.