‘Let her not, I pray, be as one dead, of whom the flesh is half consumed when he comes out of his mother's womb.'
He begged that she might not be as a stillborn baby coming from its mother's womb wrinkled, partially formed and looking grotesque, a baby that no one bothered to clean it up. For if she was permanently skin diseased she too was distorted, and was as good as dead.
(Note: ‘Leprous' is probably a misnomer. Modern leprosy was seemingly fairly rare in Old Testament times. The word means rather a general skin disease. It could also be used of mould and fungi in clothes and houses.)