The decision has been made by the USA's Food and Drug Administration (FDA) - and its decision surprisingly goes against the advice of the American Dental Association (ADA).
The ADA has told mothers that they should not mix fluoridated water into formula or foods for a child younger than one year - and so bottled water has been an obvious alternative to tap water, most of which is fluoridated.
The ADA is concerned that excessive fluoride can cause enamel fluorosis in an infant's developing teeth. Fluorosis is a condition that causes tooth enamel to discolour and pit. It's estimated that up to 32 per cent of all American children have dental fluorosis.
Fluoride in water has been linked to arthritis, allergies, kidney and thyroid dysfunction, endocrine disruption, bone damage and cancer.
And judging by the kids of America, it doesn't do much to promote healthy teeth, either.
(Source: FDA website).