It is safe to touch newborn kittens during their first week of life. This should only be done if necessary, because the mother cat may become irritated if she detects another scent on the kittens.
Kittens can be safely socialized in their second week of life. Socializing is accomplished by handling the kittens for a limited amount of time per day. Pet the kitten or by simply hold it next to your body as a source of warmth.
Kittens should be placed back with their mother after the handling process has been completed for the day.
Prior to handling the kittens, hands should be sanitized or washed. This will keep the kittens from becoming sick from any germs on their handler.