[mschempp]

Not sure I understand you correctly, but the study I linked shows that mother's earnings drop significantly after the First child. That has nothing to do with the significant monetary cost of children, which are added on top of that.

[snapplebobapple]

The alternative context that is probably correct is this is a cost of having kids because the kid makes the parent(s) less reliable/negatively impact a number of performance metrics and therefore make them less valuable. Families choose to make the wife the unreliable one and that is reflected in wages. "solving" that valuation pushes us further from an efficient market outcome making us all worse off. If the above is true, which I think it is, then the correct path is not compensating mothers for this cost, it's figuring out how to get families that can afford to bear said cost to have a lot more children.