There's a social norm thing going on there too. Regardless of what laws say there's what you can get from your employer. Employers are more flexible with women

There's a social norm thing going on there too. Regardless of what laws say there's what you can get from your employer. Employers are more flexible with women than men when children arrive. At a cost, sure, but if for whatever reason you want the man in the relationship to go part time to devote more time to kids, it's hard to be taken seriously in the face to face negotiation. Women are almost always taken seriously when making such a request. This expectation of the norm reinforces the norm too.