The child David had with Uri'ah's wife fell sick and died within
Answer Details
The child David had with Uriah's wife fell sick and died within seven days, according to the Bible (2 Samuel 12:15-18).
After David committed adultery with Bathsheba, the wife of Uriah the Hittite, he arranged for Uriah to be killed in battle and then took Bathsheba as his own wife. As a consequence of David's sin, God sent the prophet Nathan to confront him and pronounce judgment against him. Nathan prophesied that the child born to David and Bathsheba would die, and indeed the child became very sick.
David pleaded with God for the child's life and fasted and prayed, but the child died on the seventh day of his illness. David then ended his mourning and resumed his duties as king.
Therefore, the answer to your question is: "The child David had with Uriah's wife fell sick and died within seven days, according to the Bible."