You have never engage in my argument, as I’ve repeated time and time again, the difference lies in WHEN and HOW the responsibility is assumed. Here, I’ll make it easier for you:

In your organ donation scenario, the child is ALREADY born, responsibility is ALREADY assumed, and no matter what happened, both side of the parents, assuming both voluntarily engaged in parenting, has to provide for the children, regardless of their decision (which should also be voluntary) on the donation. This is because you fundamentally cannot exit duty of care recklessly, it’s negligence/abandonment. You cannot be negligent or abandonment to someone BEFORE duty is established.

And in the case of pregnancy, the duty of care (financially) is forcibly imposed on the father pre hoc.

If the father agree to the child, and want to leave the mother and child, then they should keep paying child support. Same as if the mother leave the father and the child. Because in such cases, the duty of care is already established, and both sides CANNOT relinquish their duty post hoc.

Or, if for whatever reason, in a reasonable timeframe before delivery, the mother decide to carry the child to birth on the condition that she will not assume any duty of care, and will leave the child and the father immediately after giving birth, and both sides agree, then the mother would not bear any duty, because that’s the pre hoc arrangement for the child to be given birth.

Your analogy has no relevance whatsoever to the core issue here. I don’t care what sex the involved party is, I do not support exiting duty of care recklessly AFTER voluntarily taken up the duty, the key issue is being forced into a duty you did not consent to before the fact.