In Denmark, at least. The data from a big new Danish survey:
Women who don't have children continue on the same trajectory as men, and in fact earn a little more, I suppose because many women who don't have children are highly educated and/or strong careerists. But women who have children fall off that trajectory and never climb back. More detailed data shows that mothers work fewer hours than men or women without children, more of them leave the work force, and they get lower pay, and the sum of all these is the decline you see in the chart.