> They usually retire from work mid-career for pregnancy and possibly for a much longer time to raise the child…

No. Here's how it actually works in a modern family unit in a high-earning, dual-income Silicon Valley household:

Mommy takes time off when babby is born, as does daddy because it's not 1960. At some point during this sabbatical help is hired, and then mommy and daddy go back to work and establish their new work/home balance. The end.

It's not conceptually that different than sabbaticals not involving babies. It certainly doesn't explain systemic pay discrimination.

Sabbaticals also hurt careers. You don't get a raise and a bonus for being away 1 year when you are 25-30.

This affects negatively many future years of income, because your future prospects are affected by your current job.

This is a strange position. On average every person should raise a family for the continuation of the humankind. Therefore this should affect everyone equally.

On average it affects all women equally because women are physically affected by the specifics of having babies. However, some men just choose to sacrifice their family life instead of lowering their pay rate one iota.

So you should see an effect on family income but divergences in gendered income.

> Sabbaticals also hurt careers.

I'm sure sabbaticals (and even vacations) hurt careers in some scenarios, at some companies. I was responding to the notion that this was "retirement", and unique to the woman.

> You don't get a raise and a bonus for being away 1 year when you are 25-30.

People take parental leave for weeks (6-8 is typical), not a year.

Nobody argues that there is no cost associated with the choice to have kids.

Funny, I have a buddy there with two kids and a stay st home wife.

Clearly more men need to take time off work to help raise their children.