No, it is not entirely safe...and can be hazardous in some cases. The two types that actually work are hormonal and surgical augmentation. With hormonal augmentation, you're messing with your body's natural hormone levels to try to get it to do something it's not really made to do. For the other, every time you go into surgery you are taking risks, and so it is recommended only to take those risks for necessary procedures. While they are rare, there is the chance of antibiotic-resistant bacterial infections. In addition, everyone has different reactions to anesthesia and could even have different reactions to the same anesthetic at different times. An allergic reaction to these is life-threatening, and a hyperthermic reaction can even cause brain injury. Hypothermia is also a risk, since you're putting that in the hands of the anesthesiologist or anesthetist, but that risk should be minimal since they wouldn't be opening up any major arteries or your chest cavity.