The three most important risks to discuss in breast augmentation surgery are bleeding, asymmetry, and capsular contracture. Any time any surgical procedure is performed, there's a risk of bleeding.
The risk is very low, especially in breast augmentation surgery, and especially if the procedure is performed by a board certified plastic surgeon under direct vision. There are small blood vessels and any bleeding is stopped. Therefore, the risk in qualified hands, of bleeding is very small. The biggest risk in breast augmentation surgery is not really a risk, but it needs to be thought about and discussed. All breasts are asymmetric. We tend to consider them sisters, not twins. So, every woman starts with asymmetric breasts, and every woman is going to end with somewhat asymmetric breasts as well. We attempt to make them as symmetric as possible.
There are things we can do to increase breast symmetry: changing the size of the implants, lowering or raising the lower border of the breast or the inframammary fold, however, there is a risk of the need for a reoperation due to asymmetry in a small percentage of patients.
Finally, the most discussed risk of breast augmentation surgery is known as capsular contracture. Any time any sort of foreign body is put into the human body, the body tends to form a wall or a capsule around it because the immune system recognizes it as foreign and wants to block it off from the rest of the body. In the case of a breast implant, the body forms a breast capsule. Sometimes this capsule becomes overactive and squeezes on the implant, causing what's called capsular contracture. There are different ways to treat it, but sometimes women have to go back to the operating room in order to have the capsule removed and the implants changed into a different location. So, those are the three most discussed and probably most well known complications of breast augmentation surgery.