You may not be satisfied with the appearance of your breasts after implants. Your plastic surgeon has limited control over the final shape, which is ultimately determined by how your chest, your breast, and the implant all fit together. Incorrect implant size, excessive scarring, and misplacement of implants may interfere with a satisfactory appearance. Asymmetry (unequal breast size or shape) may not be totally corrected even by different sized implants. The implanted breast may sag or droop (ptosis) over time, much like a natural breast.
While plastic surgeons can make dramatic improvements in one's appearance, you must remember that they are not miracle workers. Your anatomy dictates what your final results will be.