John Gee argues that Isaiah 7:14 cannot be a prophecy concerning the birth of King Hezekiah as he would have been between 9 and 12 years of age at the time of the prophecy.
John Gee, "'Choose the Things That Please Me': On the Selection of the Isaiah Sections in the Book of Mormon," in Isaiah in the Book of Mormon, ed. Donald W. Parry and John W. Welch (Provo, UT: Foundation for Ancient Research and Mormon Studies, 1998), 90n18
Both George D. Smith and Avraham Gileadi have taken this as a prophecy of the birth of Hezekiah, not Jesus (George D. Smith, "Isaiah Updated," in The Word of God: Essays on Mormon Scripture, ed. Dan Vogel [Salt Lake City: Signature Books, 1990], 115-9; Avraham Gileadi, "A Holistic Structure of the Book of Isaiah," [Ph.D. diss., Brigham Young University, 1981], 37). This is impossible. Ahaz reigned sixteen years (2 Kings 16:2; compare 2 Chronicles 28:1) to be succeeded by his son Hezekiah who began ruling at the age of twenty-five (2 Kings 18:1-2; compare 2 Chronicles 29:1). The date of the prophecy to "the days of Ahaz ... king ofJudah" (Isaiah 7:1) presents a major chronological problem for this hypothesis. Even though Pekah was in the last three years of his reign when Ahaz took over the Judean kingdom (see 2 Kings 15:27; 16:1), Hezekiah would have been somewhere between nine and twelve years old; it would have been too late for Isaiah to have prophesied his birth or when he would start talking.