I suppose it depends on how one defines innocence.
I checked online and "innocence" is defined as: "The state, quality, or virtue of being innocent, as:
- (a) Freedom from sin, moral wrong, or guilt through lack of knowledge of evil. (
Guiltlessness of a specific legal crime or offense. (C)Freedom from guile, cunning, or deceit; simplicity or artlessness. (D) Lack of worldliness or sophistication; naivet・ (E) Lack of knowledge or understanding; ignorance. - Freedom from harmfulness; inoffensiveness." (dictionary.com)
I don't believe they're the same, but for some reason the two words are often interchanged. Watching one's first porn movie, then, is a loss of innocence. I'm interpretting the spirit of the definition as 'losing one's innocence' is synonymous with 'losing one's ignorance'.