There is a pain so utter — Childbirth

There is a pain-so utter-1
It swallows substance up-
Then covers the Abyss with Trance-
So Memory can step
Around-across-upon it-5
As one within a Swoon-
Goes safely-where an open eye-
Would drop Him-Bone by Bone.
(F.515/J.599)
[1] pain:: pain of childbirth; pain of raising a child.
[2] swallows substance up:: to support the growing of the baby.
[3] Abyss:: a bottomless depth, the mother's devotion to the child. Trance:: the half-conscious state of how the mother feels about her child.
[4, 5] Memory, across:: of raising her son.
[7] open eye:: to see clearly her son's naughty or rebellious acts.