Have your doctor show you photos
The 600-650 high profile implants will give you a very full and round "look" and may be the right implants if their base dimension fits your own chest wall diameter. Work closely with your surgeon who can show you photos of results he or she might think would be sililar. Also, you can try on implants in clothing if they have any samples of high profile styles. Remember that the implant in your clothes will look about 20% larger than it will when it is in you.
Although it is not likely for both implants to leak simultaneously, it could explain the significant change in your breast size from DD to C. Otherwise, I am at a loss to explain this. At any rate, it may be that you need 600-650cc to achieve a large projecting breast, depending on your body type. Close discussion with your surgeon will determine your needs. Good luck!
Volume is only part of the issue
Implants come sized by volume, width, projection or profile, and shape. It becomes a judgement as to what will produce your desired post-op appearance. This is dependent on what you have to begin with. There are always trade-offs to decisions you make. You might in fact require a certain implant to give you the look you want and it may turn out to be 600ccs. There are consequences to having implants that are large weight-wise and that are disproportionate to your native breast and chest size. If these consequences are not acceptable to you, you might need to change your desires. You and your surgeon need to discuss all aspects of the procedure and all side effects and risks. in general, use the smallest implant that will make you happy.
600 cc's breast implants are too big for ANYBODY.
In New York City, as you can imagine, we see a lot of breast implants problems. And too big is probably the worst. Don't go this route. Huge implants stretch your tissues and age very badly.
Breast Implants and sizes
The larger you go with implants, the more risks of problems to develop. This is a personal choice that you have to make. But if you are only measureing a D and want DD then you probably need to make that jump in volume.
600-650cc breast implants are kind of large
They are on the large side, but to get a noticeable change in size you need to go at least 100-150 cc larger than where you are starting (when you are exchanging implants.) This is assuming that your weight is stable. If you are planning on losing weight, wait until after this is done before choosing more implant surgery. Also sometimes to get a more rounded result, you might benefit by breast lift surgery to move your own breast tissue in relation to the implants.
650ml Implant Is Quite Large
Confussed: Without the advantage of your surgeon's exam, history, and evaluation of you through the changes you describe, I cannot tell you whether such a change is something you would like.
I can suggest that 650ml size implants are rather large in proportion to a potential patient's own breast tissue coverage. Large implants are associated with increased thinning of your tissues. I suspect you will be more likely to experience sagging over time. If various complications do occur, they can be multiplied with large implants.
The look you want may be difficult to obtain (and keep).
Different implant type and size
If you already have 400cc implants and would like to be fuller, you will need an added 100-150 cc at least to feel a difference. Changing the implant type will give you also a more desirable shape. If you feel pointy and less rounded, you might want to try a moderate plus implant. This will give you a little less projection and more roundness. Again, I try to spend as much time as possible on checking the size so it would be right. Best of luck!
Sometime after having a baby, breasts deflate in the upper pole due to weight fluctuations. Has your weight changed after the implants were placed? If so, maybe a lift could be in your future to help restore the shape and allow for a perkier, fuller breast without relying upon only the size of the implant. Also, there are now super-high profile implants available that may be able to increase the projection without increasing the overall size (or #of cc) of the implant.