John Gill Commentary Numbers 12:12

"Let her not, I pray, be as one dead, of whom the flesh is half consumed when he cometh out of his mother`s womb." — Numbers 12:12 (ASV)

Let her not be as one dead
As she was in a ceremonial sense, being to be shut up and excluded from the society of people, and as defiling by touching as a dead carcase; and, in a natural sense, her flesh, by the disease upon her, was become as dead flesh, putrid and rotten, and unless miraculously cured it would issue in her death:

of whom the flesh is half consumed, when he cometh out of his mother's
womb ;
like an abortive, or one stillborn, that has been dead some time in its mother's womb; and therefore when brought forth its flesh is almost wasted away, or at least half consumed: and in such a plight and condition was Miriam already, or quickly would be, through the force of her disease.