My breast size is 40DD, it is possible I can go down to a B cup?

At
size 40, each 300 cc’s corresponds to one cup size.  To go from a DD to a B, would require 900
gram removal.  The better technique I
recommend is The Bellesoma Method.  Pain
is relieved by transferring the weight of the breast to the underlying
pectoralis major muscle so you do not need excessive reduction to be pain
free.  This allows you to keep your
breasts proportionate to your body.Best Wishes,Gary Horndeski, M.D.

Hi and thanks for your questions. After reviewing your description, it seems that that you would be a good candidate to have a breast reduction and lift using the Bellesoma technique.   More than likely you will end up larger than a B-cup, as it is also very difficult to maintain breast tissue flap and nipple-areolar viability if attempting to remove enough tissue to go from an DD-cup to a B-cup.  This is important to discuss with your board certified plastic surgeon.
Bellesoma is a new breast reduction and lift technique that seems like it would be a great fit for you.  This procedure utilizes 3-D volumetric scanning and a multi-point measuring system to design a precise surgical blueprint exactly tailored to your body and the reduced breast size that you desire. The Bellesoma procedure reduces the sagging and weight of your breast, lifts your breast and reduces areola diameter, preserves the nipple sensation, and looks as full and perky as if an implant had been placed without using any implant, so no need to compromise.  One of the huge positives of this technique is that there is no vertical incision traveling down the front of your breasts.
Some of the differences between Bellesoma and the traditional breast reduction/lift techniques:
-Bellesoma creates upper pole fullness that traditionally needed an implant to achieve.
-There is NO vertical scar, only well-hidden scars in the fold under the breast, and around the areola.
-The breast is dynamically supported by attaching it to the muscle, so there is no recurrence of sagging which are expected with traditional lifts or reductions.
-The entire central portion of the breast is undisturbed, so nipple sensation remains intact and is very unlikely to be compromised.
-For absolute best results, patients should have a stable weight and have a BMI under 30.
The procedure is accomplished by using the skin of the lower pole of the breast (the part below the nipple that sits in the bra cup) to shape the whole breast into a perky dome, then straps are made of the extra skin, anchoring it to the underlying chest muscle so that there is virtually no chance of repeat sagging.  The skin that above your nipple and below your collar bone is utilized to cover the perky, lifted dome that has been created and then a new (usually smaller) circular opening for the areola is placed at the high point of the cone, creating your new lifted, full and shapely breast.
From your description, you seem to be a very good candidate for this new technique and should really get the look that you are desiring without implants or unnecessary visible scars. I would recommend that you search for an ABPS board certified plastic surgeon who is also a member of the American Society of Plastic Surgeons and the American Society of Aesthetic Plastic Surgeons in your area or an area that you would like to travel to on holiday who offers the Bellesoma technique to discuss your breast reduction and possible results.
Best wishes!
Daniel Brown, MD, FACS 
Diplomate, American Board of Plastic Surgeons Member
American Society of Aesthetic Plastic Surgeons Member
American Society of Plastic Surgeons 
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Cup sizes are difficult to predict.  It is possible to reduce breast size dramatically with breast reduction surgery and it is important to leave behind enough healthy tissue.  I do believe that you can be very happy with a breast reduction and if your surgeon knows you want to be as small as safely possible, you can have a substantial reduction in breast size.  As you know, you can wear several different size bras that fit.  You sound like a good candidate for a breast reduciton