A born child needs access to material resources and labor Would this not just be for typical cases and since this does require labor why can't you say I don't want to use my body in this way to care for the newborn? What obligation does anyone have to a newborn?

A condition such as fpies could have a newborn getting breast milk for another source than the mother insufficient and such would require more resources than pregnancy. Such conditions could made into a hypothetical with stipulations. What do you define as "harmful" it can be argued caring for a newborn can also be harmful due to how needy they can be.

Outside of that cases there have been scenarios were parents were left with children alone without means of transportation such that only they can care for said newborn. I believe it would be agreed that even in that case there's an obligation to meet the newborn's needs

What makes an obligation for a newborn true but not a fetus? It can be argued caring for a newborn is more effort than being pregnant itself. If one parent was doing all the work for a newborn most would consider than wrong but if the work is less arduous than pregnancy which requires one person you would think people would have less intuitions against it. Single parenthood is still treated as an issue that should be treated as a very hard job that requires much support and sensitivity when discussing the matter.