" If the Child Jesus were born in the "normal" way, why would Isaiah think that qualified as a miracle possible only to God? (See Isaiah 7:14)
See my posts# 676 & 687 above."
Because The Theotokos never knew man. Are you saying He just sort of appeared in that cave in Bethlehem?
Isaiah foretold a THREEFOLD sign to King Achaz:
1) That a virgin would conceive a Child.
2) That a virgin would bring forth a Child.
3) That the Child would be "God with us."
The miracle of the Theotokos conceiving without knowing man covers only the first part of the sign.
The miraculous nature of the Child's delivery covers the second.
Catholic teaching is that the Child left Mary's womb to appear in her arms miraculously, to fulfill the second part of Isaiah's prophecy, confirmed by Matthew.