My Implants Are Not Quite As Large As I Had Expected.

Two things happen and seem paradoxical. As as the swelling goes down there will be some shrinkage but at the same time as the muscle relaxes your breast projection grows. In general the breast shape and size proportionality improves..Breast implants initially after surgery when placed in a submuscular position often give superior fullness that corrects itself with time, the "fluff and drop" phenomena. In reality the pectoralis major muscle takes a while to adjust its size to accommodate the implant as well as occasional muscle spasm which keeps the implant projection higher than its final resting shape. Additional variables include:laxity of skin, size difference during prior pregnancies, position of implant,size of muscle, and size of implant.As the muscle relaxes the projection of the implant often increases and the breast shape improves. Massage and use of a superior placed elastic strap can often make this process go faster.

The muscles and skin are very taught over the implants initially.  Over the next few weeks, the tissues will relax and the implants will settle.  Your impression of the size might change once everything has had a chance to settle. 
Your devices should increase your cup size by approximately 2 cup sizes once everything relaxes.

Breast size will not increase that much, especially once the implants drop.  it depends how high your implants are at the moment.  Three hours after surgery is not enough time to see your final result.  If you are unhappy with your results, talk to your surgeon regarding a revision. 

At 5'2" tall and 126 lbs, you are a petite woman, and 450cc implants should be expected to add nearly two cup sizes to whatever breast volume you started with. Of course, if you have little breast tissue of your own, adding two cup sizes may make your post-op size only a B to C cup.

How to choose breast implant size is one of the most common questions on this site, and in my office consultations. Please read my article "What is the Right Breast Implant Size for You?" for a more detailed answer to this question, which is something you and your surgeon should have done before your implant size was selected.

As far as what to expect now, you probably are somewhat "high and tight" in addition to which the tissues around your  breasts are swollen. This settles and resolves over several weeks, during which time your breast skin and muscles covering the implants will stretch and soften. This will make you breasts softer, somewhat more teardrop in shape, and with improved definition in the crease area. The overall net effect in some patients is that the breasts look and feel much more natural, and perhaps appear somewhat larger. This does not occur if your surgeon uses a technique that has significant swelling and bruising, uses a drain (for the same reasons), or if you develop capsular contracture. Then you could look higher, tighter, and feel more firm long-term.

Before consideration of exchanging implants to a larger size, I would recommend a wait of at least three months, and even better, 6 months, before requesting re-operation. You will need an increase of about 125cc for an additional 1/2 cup size, or even implants around 700cc if you want a full additional cup size larger (if your anatomy allows).

With your small body frame, 450cc implants would be expected to make a significant difference. This size implant is not small and a 1 1/2 to 2 cup size increase in your breast size would be normal. At 3 hours or 3 weeks after surgery, the statement that they were much smaller than you expected is not going going to change when any further implant settling and tissue relaxation takes place. If you still feel this way, it is apparent that there has been some lack of communication on expectations with your plastic surgeon. I would give it some time to adjust to the results of your surgery, preferably 3 months, and then go back and discuss your concerns at that time.