This research, which appears in Environmental Health Perspectives, is based on the observation of nearly 300 mother-child pairs in Mexico. The researchers observed the children for the first 12 years of their lives to learn more about their cognitive abilities. They kept in mind that fluoride is not added to public water supplies in Mexico, but that it naturally occurs in water and can be found in things like salt, milk and dental products.
After measuring the amount of fluoride found in maternal urine output, researchers found that levels of fluoride exposure early in life didn't appear to affect IQ, but prenatal exposure did—and for every 0.5 milligram-per-liter increase beyond 0.8 milligrams per liter, intelligence scores dropped among subjects.
Surprising, right? But it's important to remember how vulnerable babies are while they're in utero, and that even things that seem innocuous could affect them. "Childhood exposure to fluoride is safer than prenatal. There is pretty good science now to support the fact that the fetal system tends to be more sensitive to environmental toxicants than once the child is born," lead author Howard Hu told CNN.
Of course, fluoride does carry health benefits—as you know, it can prevent dental cavities (and dental hygiene is incredibly important during pregnancy!).
It's important to remember that this study was based on one population, and the relationship between these two factors may have been coincidental—we definitely need to see more research in order for this link to be confirmed.
So what's a pregnant woman to do where fluoride consumption is concerned? For now, we'd urge you to chat with your doctor if you're concerned about this news at all.