absolutely, yes it is.  Have experienced it in my business.  Costs employers tens of thousands of dollars each time it happens.  The temp worker may be incredibly difficult to find, then cost a lot to train.  and then there are the histrionics when the temp worker has to leave as the new mom comes back. And why does government assume there is a nice supply of educated skilled people waiting to take a temp job??  I can tell you it is 20x easier to hire a person for a full time long term career position than for a mat leave temp job!