The critics have labelled it slow, bloated and joyless. The Guardian's own Peter Bradshaw described it as an "emo-operetta" that "sweeps us away on a riptide of mawkish euphoria". Yet it transpires that the latest Twilight picture may possess a power that was somehow missed by its early detractors. It is now being blamed for triggering epileptic seizures in filmgoers across America.

Brandon Gephart, from Roseville, California, was reportedly rushed to hospital after falling ill during the movie's climactic birthing sequence. "He was convulsing, snorting, trying to breathe," his girlfriend Kelly Bauman told reporters from CBS Sacramento. "He scared me big time." The screening ended prematurely following the arrival of paramedics.

Elsewhere, ABC4 in Salt Lake City ran the story of an unnamed Utah man who suffered a similar seizure while watching the film. "I didn't really remember what happened after that," the man explained. "I think I blacked out. According to [my wife] I was shaking and mumbling different noises."

Fortunately his wife was on hand to paint a clearer picture of the situation. "I was kneeling in front of him and slapping his face," she said. The alleged Utah victim refused to give his name because he said he feared he would lose his job if his identity was known.

The Twilight Saga: Breaking Dawn – Part 1 charts the fraught pregnancy of young Bella Swan (played by Kristen Stewart), who is carrying the child of her vampire husband. Medical experts have suggested that the birthing scene's strobing red, white and black imagery may have triggered episodes of photosensitive epilepsy.

"It's like a light going off because it hits your brain all at once," Dr Michael G Chez told CBS Sacramento. "The trouble with theatres is that they're so dark, the light flashing in there is more like a strobe light."

Back in California, hapless Brandon Gephart pointed out that he only attended the screening to placate his girlfriend. He has no plans to revisit the movie to see how it ends.