At least when it comes to maternity/paternity benefits according to the following article:
Nonetheless, she said, “We hear very, very persistent reports that women return from maternity leave and find it very difficult to get work, even if they return to work full-time. If they return on a reduced schedule, the problem is sometimes even worse.” She added, “A not-uncommon pattern is for a woman to return, find herself unable to get enough billable hours, and then end up being let go.”
“Some of this is benevolent—‘Oh, I don't want to overload her,’” Williams explained. “Some of it is less benevolent.”
Read the complete article at: http://www.newrepublic.com/article/114026/why-big-law-firms-lag-behind-parental-leave# 
Does anyone have first (or second) hand knowledge of how law firms treat pregnant employees? Do you think that they are behind the times when it comes to family leave?