According to US reports on Friday, a graphic scene in which heroine Bella Swan gives birth to a human-vampire hybrid has sparked seizures in audience members, causing some to black out and have trouble breathing.
CBS Sacramento reported that a local theatre had to cancel a screening of the movie when Brandon Gephart suddenly started convulsing during the scene and had to be rushed to the emergency room by paramedics.
A similar incident occurred during a Utah screening in which a man who had no history of seizures blacked out.
Medical experts said a lighting effect in the scene, in which red, black and white strobe lights are used, could trigger episodes of photosensitive epilepsy in people who are genetically predisposed.
"It's like a light switch going off, because it hits your brain all at once," Dr Michael Chez told CBS Sacramaneto.
Similar effects were noted in 1990 when the Pokemon movie sparked epileptic attacks in some young viewers, while several people were reported to have passed out during a gruesome scene in last year's 127 Hours.