Why's it relevant? Why not just judge based on the employee's actual output? It's certainly conceivable that a talented and dedicated woman could both raise kids and simultaneously out-code her male colleagues.
https://www.bls.gov/opub/ted/2015/mobile/time-spent-working-...
Of course if a woman produces more output or is better, she should be paid more. My point is about how you should expect the average result to be in men's favor though, unless you think women are innately superior. If you work 8 hours a day and I work 9, I'll probably be ahead of you at the end of the year, unless you're a lot better.