Congratulations
As previous posters have said, basic will cover all the costs. Some of the benefits of having extra insurance are:
You may choose a different hospital - in my case i didn't like the reputation of my local hospital, because i had extra insurance i was allowed to give birth in the hospital of my choice (in a different kanton)
More scans, you get a standard 6 or 8 scans (cannot remember) the basic will cover more if there is a underlying health issue that requires more scans. But if you just want to have more scans simply because you want to see baba more often, basic won't cover it.
Sometimes extra insurance packages may allow you a private room after birth.
I am sure there are more, these are the ones i am experienced with. But seriously standard insurance will give you extremely good care for you and baby.
Enjoy this special time