A: To put things in perspective, remember that it's an excess of fluoride that is dangerous. You shouldn't worry or suffer a lot of maternal guilt thinking that you might have endangered your baby's health by giving her tap water to drink. For decades, mothers were advised by dentists and pediatricians to give their babies fluoridated tap water to prevent dental cavities later in life. In recent years, however, researchers have found that fluoride in infancy isn't necessary, and if babies get too much of the mineral, it can increase the risk of a condition called fluorosis. While most cases of fluorosis are mild, causing a few white spots or patches on the teeth, more severe cases can cause a brownish mottling and weaken the tooth enamel. These cases are almost always caused by fluoride supplementation or ingestion of toothpaste, rather than just drinking city water! But because of the risk for dental fluorosis, and the lack of evidence demonstrating a true benefit to children who ingest fluoride before their teeth erupt, the American Dental Association now recommends that children under 12 months of age should not consume fluoridated water.
Again, you shouldn't be hard on yourself, because this is a relatively new recommendation. For decades, mothers have been giving their babies fluoridated city tap water with no ill effects. Chances are excellent that when your daughter gets a mouthful of teeth, they'll be perfectly pearly white.