Parental obligation does not arise because the parents have harmed their child. Rather, it arises because of the general obligation not to endanger anyone without their consent, and, if we do, to ward off actual harm. Conceiving a child and getting pregnant is generally voluntary for both parents. However, the situation is never voluntary for the child. Top be a captive is to be unable to fend for oneself and thus, to be in need of protection from harm.
Pregnancy is automatically protective to the child.
Termination of pregnancy terminates the protection and gravely endangers the child. But not wanting to be a parent does not excuse us from the obligation to protect the children we cause to exist. The right to choose does not exempt anyone from the non-aggression obligation. Still, eviction is clearly gross negligence, and if it results in harm, all who participated in the eviction caused the harm and violated the non-aggression principle. The first question in abortion is, of course, personhood.