210cc Silicone Implants, Under the Muscle, Mod Plus on a Petite 5'1 90lb Body?

Thank you for your question. The most important factor when sizing implants, is working closely with your surgeon, in person, to find the implant size that gives you the look that you desire. I would try on implants in a bra to find the size that you like. I find that most women know they have found the right size when their breasts come into balance with their shoulders, waist, hips and buttocks. Unfortunately, online recommendations will not be that helpful. 

At size 32 each 100 cc's of implant corresponds to 1 cup size change.  To go from a AA to a B would require approximately 200 cc implants.  However, you have not provided any photographs and there are other aspects to consider such as skin tone, nipple position, position of the breast on the chest wall and symmetry.  You may be a candidate for a new technique called Breast Augmentation with Mini Ultimate Breast Lift.  Using only a circumareola incision it is possible to reshape your breast tissue creating upper pole fullness, elevate them higher on the chest wall and more medial to increase your cleavage.  Through the same incision, an implant can be placed retro-pectoral.  Aligning the areola, breast tissue and implant over the bony prominence of the chest wall gives maximum anterior projection with a minimal size implant.  Smaller silicone implants are more stable long term, look and feel more natural, are less likely to ripple or have complications that need revision.  Implant profile is irrelevant in the retro-pectoral position since the muscle compresses it.

Best Wishes,

Gary Horndeski, M.D.

If you think of five cc's being roughly a teaspoonful of fluid then you are talking about a very narrow range here.  I really don't think you can go wrong no matter which size you choose.  Two things to consider, however.  First, if you are going to err, I would suggest erring on the larger side.  This will be a change in your body image and your first impression when you see your result should be that you went too big.  After the implants have settled over the course of a few months, however, you will become accustomed to them, any swelling will have resolved, and the implants will have settled into position.  It is not unusual for patients at this point to wish that they had gone bigger.  I see a lot more patients who wish they had gone bigger over time than wish they had gone smaller.  Second, different doctors have different ways to determine which volume to use.  Some doctors hold up sizer implants or use bras, some make measurements of the breasts.  These are all nice, but the only way to truly see what an implant is going to look like in place is to put one in place and see what it looks like!  Unfortunately, you are asleep at this point and can't offer an opinion.  In my practice, I use disposable sizers that I use to help create the pocket for the final implant.  I can also fill these sizers up to the volume we expect to use and see what that volume will actually look like in place before we open an expensive implant.  If we need to adjust the volume up or down slightly, this is where we make that determination.  I always tell my patients that we might fine tune our final volume based on what we see with our sizer.  It might be that your doctor can do this as well.