The most important thing is to choose a bra that fits properly and supports the weight of your breast form adequately. You might find you feel more secure wearing a pocketed mastectomy bra that is designed to hold a breast form. There are many beautiful styles to choose from, including under-wire styles if that's what you prefer.
You may find that you can adapt the bra you were wearing before surgery. Bras that reveal a lot of cleavage may no longer be suitable as the breast form needs to be contained within the bra for security.
