Petworth kitten food has the proper nutrition kittens need for the first year. Then they should be have 1/2 kitten and 1/2 either lean cat food (for indoor cats) or adult cat food (for cats that live indoors and outdoors). After the first year, transition to all adult food.
This food is not just for kittens. Pregnant cats should eat kitten food throughout their entire pregnancy until the kittens are weaned. Talk to your Vet, and show them the ingredient list before starting any other vitamins.