Well I know what a strobe light is, so would not compare it to a typical strobe effect in intensity; but then I would not notice if I was not effected by it as some apparently are.
Still that being said, there was not "a graphic birthing scene". That is what I was hung up on as in the description of the "birthing scene" where in that timeframe of the film, the audience member hit the floor.
I guess we have beaten this dead horse to death. :)
Watch this
http://www.youtube.com/watch?v=35oJxdj2F_Y&feature=player_embedded
See how little it took to send nearly 700 Japanese kids to the hospital.