Some sweater patterns are designed with no front waist shaping - like Coracle, Cushing Isle, Parker Head, and more. If you're working from a design that does have waist shaping, including a Build Your Own design, no waist shaping on the front is often intentional.
For certain body types, we give you some more width on the front of your sweater in the bust. And in some cases, this places more than half of your waist measurement on the front of your sweater, too. And once we give you the appropriate amount of ease in the bust and waist, the front of the sweater becomes straight! The back shaping will easily make up for this; once seamed together, the sweater should still fit beautifully.
If you're nervous, take a look at this sweater on Ravelry -- the fronts are straight, with no shaping, and it looks great on her curves.