Frequently people become revenants through no fault of their own, as when they are conceived during a holy period, according to the Church calendar, or when they are the illegitimate offspring of illegitimate parents. Indeed, in Romania it is reported that merely being the seventh child in a family is apt to cause one to become a revenant.

Similarly, there were a number of other physical signs that people watched for at birth in order to detect children who might be potential vampires: in Slavic countries where most had dark hair and eyes, any child who was blue-eyed and redheaded would become vampires after death.

Some children were born with specific abnormalities that were meaningful to those involved in vampire folklore:

Children being born with teeth have obvious implications, as vampires are known for their sharp teeth and biting.

Similarly suspicious are children with an extra nipple; with a lack of cartilage in the nose, or a split lower lip; or with features that are viewed as bestial, such as fur down the front or back or with a tail-like extension of the spine, especially if it is covered with fur (likewise fur or a tail would point to werewolves).

Not to forget children born with a membrane covering their heads (cauls). In this case, it was possible to prevent the change by burning the caul and feeding the ashes to the baby.