I am a Board Certified Plastic Surgeon with over 25 years experience in the field. I frequently hear from patients what size should I go or see patients asking that question on portal sites for breast surgery.
Ultimately the patient is going to "wear" the implants she choses so she needs to have a good idea prior to surgery how big or small she is going to look. the simplest approach I have found for my patients is to put implants in a bra with the patient wearing a tight T shirt until they come to a volume that they like. then given their natural measurements, I can fully inform them of the risks and benefits of the size they have chosen. I frequently tell them to ignor cup sizes as it is very difficult to predict what size they will be as cup sizes change from manufacturer to manufacturer. It is best to chose the volume you like first and whether that is a safe choice for you given your anatomy.
Dr. Corbin www.thebreastexpert.com