"It's common here, that women on maternity take a correspondence course or learn languages, etc. Often they are more skilled at the time of their return."
If they can learn a language or take courses, why can't they come back to work?
You can learn a language at home by using Rosetta Stone software, and take correspondence courses also by staying at home. It's hard to take a baby to work. Small children require attention in fits and spurts that are not conducive to doing work that requires long periods of concentrated cooperation with other adults.
If they can learn a language or take courses, why can't they come back to work?