While I am NOT against implants - or any plastic surgery - I think it is an individual decision. I do think you should re-think implants for the time being.
Given your pre-disposition to large boobage, if you get implants and get PG later in life, you will be dealing with SERIOUS boobs. I am smaller than you boob-wise (only have gotten up to a full D even when heavy). And now, being not quite 11 weeks PG, my boobs are starting to REALLY grow. In started as a full C, and I bet I am a full D now. I am SPILLING out of my bras right now. And boobs aren't even really supposed to grow until 2nd and 3rd trimester! I have no doubt I will outgrow a DD before this child is born.
I would worry that with implants, and then getting PG, you would be dealing with boobs that would be totally out of control. Not to mention finding clothes to fit. Of course, that is you decision, you will look great no matter what.