If the birth and childbearing is being compensated by being able to spend time with the child, why give any consideration in any other field (say custody, parental leave, etc) if its already paid for.
Sorry, still not quite sure what you mean (I'm not a native speaker, maybe that's why).
Childbearing is of course not the only cost of having a child. Custody and parental leave just make it a bit less expensive (at least for some).
However, the initial investment is usually mostly by the mother. Other expenses come later. I think you could discuss who has the right to the kid if, say, the mother abandons it after birth and the father lovingly raises it for 10 years. I suppose that is also what happens in custody lawsuits?
I like this comparison, but only because I haven't found a better one yet:
Suppose you dream of sailing, and you start building a sailing boat. You work on it for a year, building the boat with your own hands.
The day the sailing boat is ready, your husband takes it from you, says "thank you, now you may go back to your normal career again", and sails off to unknown lands with your ship, while society applauds his sacrifice for the sake of your career.
