How dangerous would it be to get a second breast enlargement surgery?

Why?: I do not know why you would want a second breast enlargement surgery?Is is because there is scar tissue or leakage of silicone or saline?Or do u want larger breasts? Was the initial procedure dissatisfactory for some reason? Surgery has potential risks. There are always anesthesia risksyou need to decide whether the risks outweigh the benefits with your physician and a possible 2 opinion.

Not very but...: You've asked a loaded question. Secondary surgery after breast augmentation is very common and safe. However, risk is only half of the equation. The other important piece of information is, "what is the benefit?" whether surgery is entirely elective or is needed to correct a problem, the risks and benefits should be discussed with a board certified plastic surgeon in an open and honest way.