S.S.
In my experience, it depends on what size you are and how comfortable you are with a bunch of straps. If you're relatively small (lets say medium or smaller) and your belly isn't throwing quite everything off, there is a simple belt that goes around your abdomen at toys r us for something along the lines of 30 bucks or less.
I had a prenatal cradle - I'm an XL and delivered 9 lb babies - it was very strappy, quite expensive, and worth it.