Amniomancy - from the Latin 'amnion' (meaning membrane), it is a method of divination by means of the membrane which sometimes envelopes the head of a baby at birth. From the inspection of it, the diviner predicts what sort of future the newborn will have.This membrane, called caul, if red-colored signifies that the child in question will have a happy life. But if the membrane's lead-colored, the infant will have misfortunes.

In ancient Rome when a child was born with a caul it was believed to be an omen of phenomenal good luck, and in other parts of the ancient world such a person was considered to be immune to witchcraft and protected from drowning.In medieval times, the appearance of a caul on a newborn baby was also seen as a sign of good fortune. Medieval women often sold their cauls to sailors for large sums of money, because a caul was then also regarded as a valuable talisman against drowning.

A caul (Latin: Caput galeatum, literally, "head helmet") is a thin, filmy membrane, the remnants of the amniotic sac, that covers or partly covers the newborn mammal immediately after birth. It is also the membrane enclosing the paunch of mammals, particularly as in pork and mutton butchery. In butchery, the caul is used as offal.

A third meaning refers to a type of historical headress worn by women that covered tied up hair. A fancy caul could be made of satin, velvet, fine silk or brocade, although a simple caul would commonly be made of white linen or cotton. The caul could be covered by a crespine or a mesh net to secure it from falling off.

In childbirth, the caul (or veil) is seen as a shimmery coating of the head and face. The caul is harmless and is easily removed by the doctor, midwife, or person(s) attending the childbirth. A child born in this way is known as a caulbearer.

Medical sources contradict the popular opinion that a distinction needs to be made in relation to the birth caul and the adhesion of the birth (amniotic) sac to the face or head of a child at birth. In this view, the birth caul is a complete membrane covering the face of the child and the amniotic sac, or amnion, is another completely different kind of membrane that surrounds the child in the womb. The caul cannot be wiped off the child's face but must be carefully peeled off, while the adhesion of the amniotic membrane is simply a residue that sometimes sticks to the face, and is part of the afterbirth material.

Taber's Cyclopedic Medical Dictionary, medterms.com, and Dorland's Illustrated Medical Dictionary describe a caul as a piece of amnion that sometimes envelops a child's head at birth. To be "born in a caul" is to be born with the head covered by the amnion or within an intact unruptured amniotic sac.

According to Dwight Cruikshank MD, Professor and Chairman of Obstetrics and Gynecology at the Medical College of Wisconsin states that being born with or in a caul is rare, probably occurring in fewer than 1 in 1000 births, and that he has seen fewer than 10 babies with a caul over the life of his career. He says that it is usually present only in premature babies.

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. Gathering the caul onto paper was considered an important tradition of childbirth: 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. Over the course of European history, a popular legend developed suggesting that possession of a baby's caul would give its bearer good luck and protect that person from death by drowning. Cauls were therefore highly prized by sailors. Medieval women often sold these cauls to sailors for large sums of money; a caul was regarded as a valuable talisman. Other legends also developed. One popular legend went that a caulbearer would be able to see the future. A different legend held that a child born in caul would grow up to be a vampire if the caul was not disposed of properly.