The first few weeks of a kitten's life are crucial. Kittens can be very fragile and completely rely on their mother for nutrition as well as social requirements. Kittens that do not survive the first few weeks have been called "faders" or afflicted with "fading kitten syndrome." About 20 to 40 percent of all kittens born will not survive past 12 weeks of age. After reaching 12 weeks, most kittens will continue to grow and develop. Causes of kitten death in the first 12 weeks of life are generally linked to problems associated during development in the uterus, problems associated with the birth process or problems around the time of weaning.
For more information, please read Fading Kitten Syndrome