The American Dental Association has changed its guidelines and now recommends fluoride toothpaste in all children, including infants and toddlers who are too young to spit out the excess toothpaste. Previously, they recommended water or non-fluoride toothpaste in infants and toddlers.
This has been a source of confusion for years now. The American Academy of Pediatric Dentistry has recommended fluoride toothpaste at all ages, which conflicted with the ADA guidelines. Now they are both the same. I have followed the AAPD recommendations, and I am glad the ADA is finally in agreement. Some other organizations, however, have not changed, so there are still conflicting guidelines which might confuse parents.
Infants and toddlers less than 2-3 years of age should use a smear of fluoride toothpaste. Children 2 or 3-6 years old should use a pea-sized amount, and be taught to spit out the excess as soon as they are old enough to do so (the two organizations still disagree on when to change from a smear to a pea-sized amount of toothpaste).