When I was looking into my rights during my pregnancy I didn't come across anything that said you would have to pay back your maternity pay if you left your company, either voluntarily or through being made redundant (or sacked!).
I was given 16 weeks at full pay but that was probably because my boss is a sweetie

. Our company is quite family orientated.
You should also know that, in Switzerland, the maternity leave only starts the day the baby is born. I had to have 6 weeks off before the birth because of slight complications but this was classed as sick leave and I had a sick note from my ob/gyn.
This bit is actually better than the UK because there the maternity-leave clock starts ticking as soon as you finish work before the birth, although, admittedly the maternity leave is longer. The standard Swiss 14 weeks is a bit mental...
Hope all goes well with the rest of your wife's pregnancy and the birth! Then the real fun starts!