Too many of my friends and clients have been forced out of their chosen careers after returning to work from maternity leave.  It's a familiar tale - flexible working requests are refused; major projects are assigned to other colleagues; risk of redundancy letters arrive. I know too many university educated dinner ladies and receptionists who were forced out of high powered jobs by employers who perceived them to be less dedicated or more likely to take time off work once they had children.  

Often it's quite the opposite. Ask any mother working four days a week and I bet she will tell you she effectively works five days in four, checking emails and taking calls on her day off.  Perhaps if employers are made to publish retention rates for new mothers they will think twice about losing the talents of these working mothers.