Albert Barnes Commentary 2 Kings 19:3

"And they said unto him, Thus saith Hezekiah, This day is a day of trouble, and of rebuke, and of contumely; for the children are come to the birth, and there is not strength to bring forth." — 2 Kings 19:3 (ASV)

The "trouble" consisted of "rebuke" (or rather, "chastisement") for sins at the hand of God, and "blasphemy" (or rather, "reproach") at the hands of men.

The children... — that is, "We are in a fearful extremity—at our last gasp—and we lack the strength to carry us through the danger."