Do not disturb during the birth and first two days. The first 48 hours is a crucial time for the mother to bond with her kittens, so try not to disturb her. If she gives birth under your bed, leave her there. Moving the newborn kittens will distress the mother and in the worst scenario could cause her to reject them. Once she is firmly bonded, at around four or five days, if you feel it's necessary to move the kittens, do it then.