Here the author speaks of Yahweh causing the baby to become sick as Yahweh attacking the child. Alternate translation: "Yahweh afflicted the child that ... and he was very sick" or "Yahweh caused the baby that ... to become very sick" (See: [[rc://en/ta/man/translate/figs-metaphor]])
This means that she gave birth to a child and that David was his father. Alternate translation: "David's child, who Uriah's wife gave birth to" (See: [[rc://en/ta/man/translate/figs-idiom]])