Prenatal fluoride exposure raises the risk of developing neurobehavioral problems in toddlers, a study revealed.

Water fluoridation, the process of adding fluoride to drinking water, began in the U.S. in 1945 as a measure to prevent tooth decay. However, earlier studies have shown that exposure to fluoride during pregnancy could affect the IQ of the children.

To estimate the impact of maternal fluoride exposure on child behavior at the age of three, the research team at the Keck School of Medicine of USC evaluated more than 220 mother-child pairs in Los Angeles, California.

Maternal fluoride exposure was estimated from urine samples collected during the third trimester of pregnancy. The children's behavior, including social and emotional functioning at the age of three, was assessed by parents using the Preschool Child Behavior Checklist.

The results showed that children with more fluoride exposure experienced issues such as emotional reactivity, somatic complaints including headaches and stomachaches, anxiety, and symptoms linked to autism.

"Women with higher fluoride exposure levels in their bodies during pregnancy tended to rate their 3-year-old children higher on overall neurobehavioral problems and internalizing symptoms, including emotional reactivity, anxiety, and somatic complaints," Tracy Bastain, an associate professor of clinical population and public health sciences and senior author of the study, said in a news release.

The team also noted that a 0.68 milligram per liter increase in fluoride exposure nearly doubles the risk of neurobehavioral problems in children, reaching levels close to the criteria for clinical diagnosis.

"This is the first U.S.-based study to examine this association. Our findings are noteworthy, given that the women in this study were exposed to pretty low levels of fluoride—levels that are typical of those living in fluoridated regions within North America," said Ashley Malin, lead author of the study.

There are no current stipulations to limit fluoride exposure in pregnancy. The researchers hope their findings will help officials formulate one to reduce the risk.

"There are no known benefits to the fetus from ingesting fluoride. And now we have several studies conducted in North America suggesting that there may be a pretty significant risk to the developing brain during that time," Malin said.

To further understand the extent of the impact, additional studies evaluating fluoride exposure in other regions of the country are required.

"While this is the first U.S.-based study of fluoride exposure during pregnancy, more studies are urgently needed to understand and mitigate the impacts on the entire U.S. population," Malin added.