Are 310 cc round moderate silicone implants too big? I’m 5’6” and about 128 lbs. (photos)

Based on your photos I think that you have a very good chance at a nice outcome with 310 cc implants if the base diameter matches your breast width measurements.  I would not be worried about 15 cc difference as that is only a tablespoon of difference in volume.  If you liked the way the 295's looked you won't see much difference in the 310.  Best of luck on your journey.

Too big? is not a simple question to answer.
When sizing patients, there are a number of useful tools including:
-3D imaging (has the added benefit of offering a volumetric analysis of the pre-operative breast)
-Breast sizers (rice bags)
-Goal photos
I also recommend that patients commit to a particular look rather than a cup size. Once a patient settles on a look that pleases them the overall cup size increase becomes less relevant.
With regards to your specific question, the key to obtaining a natural result is to stay within the parameters defined by your BWD. This will ensure that you avoid the dreaded "fake" look. The difference between 295 cc and 310 cc (15 cc) will be difficult to distinguish post op (3 teaspoons). As long as you have been appropriately sized, you will likely do fine with either option.
I would recommend discussing your concerns with a board certified plastic surgeon (ABPS).

I appreciate your question!

After performing hundreds of breast augmentations, I have found that the size of implant best for you is dictated by your chest wall measurements. Once we determine that we can choose the profile based on what you want or need to achieve.  If you are seeking a natural look, then the diameter of the implant should be equal to or, more ideally, smaller than the width of your breast. The breast width is a measurement of how wide your breast is at the base, which should be measured at the level of the nipple. Choosing an implant that is smaller in diameter than your breast width will avoid the "side breast" fullness that is often associated with a more artificial appearance. Other than that, you should choose the implant based on volume, not on the dimensions of the implant. You should choose a board certified plastic surgeon that you trust to help guide you in this decision. Bringing photos as well can help us to finalize, but please understand that these are of other people’s bodies and your results will probably be different.

Silicone will give you fullness at the top (upper pole fullness). Silicone implants come pre-filled with a silicone gel and are the softest implant available. They feel more natural, which makes them a good option for women with less natural breast tissue; but they require a larger incision. It may be more difficult to realize if this type of implant has ruptured, so it is important to monitor them with annual follow-up visits. Additionally, because this implant contains a softer silicone (less cross-linked), if this implant should rupture, it may leak but only into the scar capsule formed. However, the newer silicone in these implants may not leak even when the implant shell is ruptured.

Anatomic gummy bear implants might be a good choice to give you a more natural look. These highly sought after, anatomic implants offer a look that more closely resembles the natural silhouette of a breast, and, therefore, is a very attractive option for individuals seeking a natural-looking, aesthetic primary breast augmentation. Additionally, these implants are an especially excellent option for patients undergoing restorative or corrective breast surgery because they provide more stability, shape, and reduced incidence of capsular contracture. Compared to other types of silicone gel implants, the silicone in the cohesive gel implant is more cross-linked; therefore, should the implant shell “rupture,” it maintains its shape and silicone does not leak.

During your breast augmentation consultation, you should feel the different types of implants available, and try on various implant sizers in front of a mirror to help you to get an idea of how you will look following the surgery. You should also bring pictures of the look you would like to achieve, as well as a favorite top to wear when trying on implant sizers. I also use a 3D imaging system to allow you to try on a variety of shapes and sizes. I prefer this method over adding volume due to implants being under the muscle.

We will also discuss the possibility of needing a lift along with an implant. This will depend on the amount of ptosis (nipple position) as it relates to your breast, inframammary crease and chest wall. Needing a lift or not will also determine where to place the scar for the incision.  In some cases if the breast and nipple is really ptotic (low) it might be best to stage the procedure by performing a lift first and then doing an implant at a second stage. This will also allow you to have a better understanding of the true size and shape of your breast.

The best way to assess and give true advice would be an in-person exam. Please see a board-certified plastic surgeon that specializes in aesthetic and restorative breast surgery.

Best of luck!

Dr. Schwartz

Board Certified Plastic Surgeon 

#RealSelf100Surgeon

#RealSelfCORESurgeon

To answer your question about 295cc, you need to take into account what's known as your base width diameter.
Imagine lying on your back and drawing a circle around your breast. If you were to draw a line across that circle, it will be a given length. Your plastic surgeon will measure this length, which is called ‘’base width diameter’’ or BWD for short. 
 
For women, the base width diameter can go from 9.5 cm to 16.5 cm, or 3.75 to 6.5 inches. As you can see, there is a very wide range. 
295 cc on a woman with a BWD of 10 cm is very different than 295 cc for a woman with a BWD of 15 cm. On one it may be enough volume, and for the other it may be much less than the max she can safely go. 
Regarding sagging, whether you have implants or not, aging, pregnancy and breastfeeding will do things to your body. When you’re pregnant, your body releases more hormones. You’ll gain weight. Your skin will be stretched by the pregnancy weight and lose some elasticity.  And after childbirth and breastfeeding, your breast will deflate and your skin will be looser. 
Now, there are two major unpredictable factors surrounding these changes I just mentioned. First, the DEGREE that these changes will occur is unpredictable. We don't know and can't know ahead of time, how much your breasts will deflate or how much looser your skin will become.
 
And second, it is unpredictable whether these changes will warrant a procedure. Maybe the deflation will be mild and not warrant a breast lift. 
 
So given these two unknowns, it is impossible to predict whether how much you will sag. But note that If you already have a breast augmentation, the implants will not affect those factors. 
I hope that answers your question the 295 cc volume and sagging. It’s great that you’re doing this research. I always say that the best patients are informed patients.
You might also want to research your options for breast implants. Choosing the right implant is the number one concern among women considering breast augmentation. Did you know, there’s actually a way to select a implant shape, size, and profile that is perfect for you?
A term that I use with my patients for the perfect implant is the “Pony Implant”.
So what do I mean by “perfect”? Well, a Pony Implant has three qualities to it. First, the implant meets your beauty goals. For example, you want to your breasts to look fuller while still appearing natural.
Second, when you chose your Pony Implant, you walk out of your consultation 100% confident that you’ve chosen the right shape and size for you. In other words, you won’t be second guessing your decision, and you won’t be afraid of having gone too big or too small.
And third, after your procedure, you are thrilled with your results, and say, "I’m so happy. This is exactly what I wanted!"
That’s the Pony Implant. And the great news is that there is a simple process to go about finding yours.
This issue of selecting the right implant is so important when it comes to patient satisfaction or dissatisfaction that, again, I really encourage you to learn more about it.
Thank you for reading and best of luck on your journey!

Thank you for the question. 
 Based on your photographs, I think that you are starting at a good place and should have a very nice outcome with breast augmentation surgery.
There are several steps taken to select a specific size/profile breast implant for a specific patient. These steps will vary from one practice to another.  I prefer to have a wide selection of implants (all profiles) available in the operating room. I use intraoperative sizers and place the patient in the upright position to evaluate breast size. Use of these sizers also allow me to select the breast implant profile (low, moderate, moderate plus, high-profile) that would most likely achieve the patient's goals. The patient's goal pictures are hanging on the wall, and allow for direct comparison. I have found that this system is very helpful in improving the chances of achieving the patient's goals as consistently as possible. 
Ultimately, careful selection of plastic surgeon and careful communication of your goals (in my practice I prefer the use of goal pictures, direct examination/communication in front of a full-length mirror, in bra sizers, and computer imaging) as well as careful measurements (dimensional planning) will be critical.
Generally speaking, the best online advice I can give to ladies who are considering breast augmentation surgery ( regarding breast implant size/profile selection) is:
1. Concentrate on choosing your plastic surgeon carefully. Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you are looking for. Ask to see lots of examples of his/her work.
2. Have a full discussion and communication regarding your desired goals with your plastic surgeon. This communication will be critical in determining breast implant size/type/profile will most likely help achieve your goals. 
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. For example, I have found that the use of words such as “natural” or "C or D cup” or "too big" etc means different things to different people and therefore prove unhelpful.
Also, as you know, cup size varies depending on him who makes the bra; therefore, discussing desired cup size may also be inaccurate. Again, the use of computer imaging has been very helpful during the communication process, in our practice.
3. Once you feel you have communicated your goals clearly, allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals. Again, in my practice, this decision is usually made during surgery, after the use of temporary intraoperative sizers.
In your case, my best advice: more communication. It will definitely worth spending more time (prior to the date of surgery) with your plastic surgeon to discuss further.  As you know, it will be important for many reasons, that you feel comfortable that you and your plastic surgeon are on the "same page" prior to proceeding.
I hope this helps. Best wishes for an outcome that you will be very pleased with.

With out seeing measurements and in person exam which is a more definitive process for making decision on implant size.  However, I feel from above photos that this size is  adequate d/t width of the implant. Projection does not increase much with these particular implants with increase in size- what does increase is the width of the implant. This gives better cleavage and upper pole volume. This seems a very reasonable size. You should go into surgery feeling confident with size and profile of implant. If any doubt you should visit with surgeon again and try on implants. Best of Luck to you!