How do they think it will risk your health?They have no problem with having cosmetic surgery on girls genitals, implants are such a non-event compared to that!
I would seriously speak with your parents and be prepared with lots of information on the risk factor of getting implants.
I know a few people that have gotten them and it is definitely a big boost to their self-esteem.
One other thing you would need to consider is that you may not be able to breast feed when you have children, and that means a lot to some people.
Good luck with your decision!
Beth