I have a 28a cup size. I’m a 29 year old female who is 5’7". I am wondering how big someone so small should go? (Photo)

Thank you for your question and photograph.  I think you are starting from an excellent position and should anticipate a nice result.  Breast implant selection is an exciting, but stressful part of the breast augmentation process as there are so many choices. Unfortunately it is impossible to recommend the best implant style, size or shape without an in-person examination that allows for the measurement of key breast parameters, as well as permits an in-depth discussion as to your desired goals and outcome. I would recommend seeing a series of ASPS board certified plastic surgeons to ensure that the implants you decide upon are the right ones to meet your expectations and it would be wise for you to "try on" several of the implants so that you can have a better visual representation as to what they would look like.  Best wishes! 

Thank you for your question and photo. The “augmented” look is one we try to avoid in all of our patients, and the most common reason for disappointment after breast augmentation is size. In our office there are three elements that go into the decision regarding implant selection, and we rarely go to surgery with only one size. First I interview all my patents to learn exactly what their goals are "in words". Then I examine and measure to see what implant dimensions would "fit" into her breasts. You cannot put a size 4 shoe on a size 8 foot. We then have an understanding of which base width would be suitable, but for that exact width there are at least 4 different implants that might fit (low profile, moderate plus, high, or ultra high) and this relates to "the look" one is trying to achieve-conservative (natural) ballerina or exaggerated "augmented" look with round and very large breasts, or perhaps something in between. We then use on lay forms that will show you what you are likely to look like in an unpadded bra. They come in 100 cc increments and one can even add a 50 cc only to be as precise as possible. Finally, we ask all of our patients to use our "What Size Should I Be" functionality on our website that allows you to plug in your height, weight, and current bra size. This will bring up all of the patients in our gallery who fit your demographic and can give you a visual idea of what you can expect after your surgery, remembering always that no two patients are exactly the same. 
The most important step for you is to determine who is the best surgeon for you based on his or her before and after gallery, and if your interaction with your surgeon and his or her office staff feels right. Finally, be sure that your own sense of aesthetics aligns with that of your surgeon. Best of luck to you.