I would not expect incontinence to occur as a result of a labiaplasty and have not personally seen this complication of surgery. Labiaplasty surgery is performed on the labia, which are separate from the structures involved in urinating (the urethral opening, the urethra and bladder).
If you are experiencing incontinence after a labiaplasty I recommend that you see your surgeon and primary care physician. You may benefit from referral to a specialist for further evaluation and treatment. If your surgery was performed without complications in a standard manner it is unlikely that persistent incontinence is related to your surgery.