No, I'd never heard of it either, but a friend's daughter is shortly to give birth to a girl with this condition, in which the upper organs (heart, lungs) are imperfectly isolated from the lower (liver, kidneys, gut). It's not a great start in life for the poor wee mite, who will have to be whipped off to surgery for emergency repair.
Anyone have experience, first- or second-hand, or medical, of CDH?