I think it's rather that you'll find control type knickers are uncomfortable & restrictive. I know I cannot stand any tight knickers now that I'm pregnant. I buy a size bigger than I need now because I hate feeling the elastic.
I don't think control knickers would be dangerous though because bubs is fairly well protected in there.
I know Bonds make maternity knickers that go over the bump which you might find "suck" you in? Haven't tried them personally though.