I think Cal's proposal deserves consideration. (It's probably still game-able.)

The problem isn't that maternity leave disrupts companies individual companies. So does sleep, and they're both part of normal human life. The problem is that the system in effect has the effect of a) discriminating against woman and b) suppressing the birth rate. If you are planning at a national level, suppressing the birth rate for a tiny economic boost right now is a high road to nowhere.