What are the chances of getting Fat embolism after a BBL?

Rate of death for BBL? It is at least 1 in 3000 but likely much greater due to under-reporting. If you are considering a Brazilian buttlift:Ask your surgeon about board certification plastic surgery – there are no other certifying boardsAsk if “under the skin” fat transfer is performed with blunt large diameter cannulae with transfer only the tissue directly under the skinAsk if the surgery is occurring in an accredited facility with a board certified anesthesiologistAsk if injection occurs when you can see the tip of the cannula under the skin
Kenneth Hughes, MD, Board Certified Plastic SurgeonLos Angeles, CA

Thank you for the questions. The current evidence suggest that the risk of fat embolism in BBL is around 1 in 3000. To put this in perspective, the risk of dying from a general anaesthetic is about 1 in 100,000There have been several recommendations to reduce this risk of fat embolism and these should be followed. If you decide to have this surgery, please make sure your surgeon follow these. These measures are thought to reduce the risk but we still do not have clinical data to tell us the exact statistics (is it 1 in 3000, 1 in 10,000? we simply don't know yet).

You are correct in that fat embolism is a known complication after BBL surgery. This happens when injecting the fat into the buttocks- the fat can inadvertently get into a punctured blood vessel and then travel up to the heart and lungs. This could be a disastrous and potentially fatal complication. There is not anything the patient can do to prevent this complication- it is a result of the technique used by the surgeon. A board certified plastic surgeon will be up to date on the safest techniques to prevent this complication: injecting superficially (NOT in the muscle), using blunt instruments, being aware of the where the instrument is at all times, etc. Consultation with a board certified plastic surgeon will allow you to ask these questions and get a sense for how the surgeon can minimize this complication. 

Fat embolus is a very serious and known complication of fat transfer (which has been recently spotlighted in the media). While it is true, injection of donor fat into the infra-muscular plane (within the muscle) increases fat viability, this does come with a significant increase in risk. There are large vessels deep to and within the muscle which can be inadvertently injected while grafting leading to a fat embolus. The consequences of such a complication are very serious and life threatening.
BBL/gluteal lipoaugmentation demonstrates a dramatically higher risk profile than other surgeries. The Aesthetic Surgery and Educational and Research Fund has convened a task force as well. The hope is that we will have more concrete guidelines for addressing these very serious complications.
That being said, the safest way to avoid fat emboli is to stay in the subcutaneous plane (at the expense of fat viability) and avoid the deeper muscular plane. If grafting of the deep plane is planned, surgeons should consider blunt cannulas and aspiration prior to injection. Using a supra-gluteal approach to minimize the risk of inadvertent intravascular injection has also been proposed. While this will likely impact graft viability negatively, it will also lower the risk of a serious complication.
According to AAASF data the risk of death from BBL will range from 1:3000 (subcutaneous grafting should reduce this risk relative to intramuscular grafting). By comparison the risk of fatal complication from abdominoplasty is 1:13,000. It is unclear how the relative risk falls with subcutaneous injection vs. intramuscular injection (however, in all likelihood, it is less).
No result is worth risking one's life for. I find that the patients who focus not on the volumization but rather the contouring benefits of the liposuction are happier than those whose sole goal is size. Relatively speaking, the subcutaneous plane is the "safe" plane.
In summary, the procedure can be safely performed, however, they should be performed by a board certified (ABPS) plastic surgeon with experience. These risks should be discussed as well as the strategies being employed to avoid them.

You are right, that is a known risk of BBL and there are currently major alerts within the US for Board Certified Plastic Surgeons. I don't see your location above but please seek only Board Certified surgeons in the US and read up on the risks. I do not perform them due to long term outcomes and risks to my clients. Best of Luck. 

I do not offer BBL in my office due to the risks associated with this procedure.  It sounds as though you are doing your homework. Please make certain your surgeon of choice is a board certified plastic surgeon.  During your consultation your surgeon will discuss the benefits and risks of the BBL procedure.  Best wishes!