My son was born in the caul i.e. the amniotic sac didn't break during the birth (Ange's "waters" didn't break).
Depending on what website you look at this occurs between one in a thousand births and one in eighty thousand births. Probably less common these days as the breaking of the sac is often done by the midwife / doctor.
Apparently it means good luck and that the person will never drown. I also found the following with regard to buddhism:
In many cultures the Caulbearers (those born in the Caul) were considered to be “Kings by right,” due to the predictive nature of their births and their leadership abilities. This is one of the reasons why certain Buddhist groups, to this very day seek out Caulbearers to be brought up to become Dalai Lamas.