An influential medical journal published a study Monday that links fluoride consumption during pregnancy with lower childhood IQs—a finding that could undermine decades of public-health messaging, fire up conspiracy theorists, and alarm mothers-to-be.

The research was expected to be so controversial that JAMA Pediatrics included an editor's note saying the decision to publish it was not easy and that it was subjected to "additional scrutiny."

"It is the only editor's note I've ever written," Dimitri Christakis, editor in chief of JAMA Pediatrics and a pediatrician, told The Daily Beast. "There was concern on the journal's editorial team about how this would play out in the public eye and what the public-health implications would be."

About three-fourths of the United States drinks fluoridated tap water—which the U.S. Centers for Disease Control and Prevention declared one of the 10 greatest public-health achievements of the 20th century because it dramatically reduces tooth decay.