I was looking for some documentation before replying, i know i have it somewhere but i've been unable to find it so far.
Anyway, there's always risk of nerve damage, the choice of incision can reduce the risk. For many women loss of sensation (partially) comes back after a few weeks to months. For some it is permanent.
Incisions around the areola have the highest risk of course.
Bigger implants can stretch the skin more and restrict blood flow.
However, it's also funny to mention that a considerable amount of women report an increase of sensitivity.
From personal experience i can say that my GF's boobs have suffered considerable nerve damage of which only some has returned, she still has numbness around the cleavage area, so her nipples are fine, but it feels weird to her not having sensation in the middle area.