If a Brazilian Butt Lift is performed properly, carefully and by a surgeon certified by the American Board of Plastic Surgery it should be safe but not risk free.
Immediately after it is injected, and for several weeks post-operatively, the newly injected fat does not have its own blood supply and is quite fragile. During this time some of the fat will die and not contribute to the new shape.
Sometimes when the fat dies (necrosis) it can leave a firm or hard area of scar tissue or actual calcification behind.
As with any surgery, there is the potential for post-operative bleeding (hematoma) or infection requiring treatment.
Because several areas are often liposuctioned, and in order to provide enough fat, there is the chance for contour irregularities in these areas.
One of the most serious complications, although very rare, is a fat embolism. A fat embolism occurs when the injected fat gains access to a larger vein allowing it to travel to the lungs. This can occur if the fat is injected deeper than the buttock fat layer into the muscle layer. It can also happen when too much fat is injected causing too much pressure in the receiving area. For these reasons it is critically important to have your procedure performed by a surgeon who is properly trained and certified by the American Board of Plastic Surgery.