New-born with a caul;A caul (Latin: Caput galeatum, literally, "helmeted head") is a piece of membrane that can cover a newborn's head and face.Birth with a caul is rare, occurring in fewer than 1 in 80,000 births. The caul is harmless and is immediately removed by the physician or midwife upon delivery of the child.In medieval times the appearance of a caul on a newborn baby was seen as a sign of good luck. It was considered an omen that the child was destined for greatness. The midwife would rub a sheet of paper across the baby's head and face, pressing the material of the caul onto the paper. The caul would then be presented to the mother, to be kept as an heirloom.