This is a matter of statistics and risk evaluation, it is a fact that health insurance companies take the risk of pregnancy into account when calculating the in

This is a matter of statistics and risk evaluation, it is a fact that health insurance companies take the risk of pregnancy into account when calculating the insurance premium, whether you like it or not. In the same way there is a risk to the employer and in principle it is fairly easy to assign a cost to it, too. For example, assume an employee makes 40k a year and will take 3 years off during her work life, due to pregnancy (not uncommon in Europe and often with almost full compensation). Assume she works 40 years, then the cost per year is 3k, so she should actually be compensated with ~37k per year. This is the most naive calculation, if you knew statistics on how many men vs. women take paid leave because of children and so on you can of course come up with a much better cost model. If you assume that a company acts rationally there is no reason for arbitrary discrimination, but every reason to adjust wages according to possible costs. I'm sure in the case of wage inequality, this is not the main reason however.