I used to believe that Old and New Testaments were one united work, but on closer examination it seems like in a lot of instances the NT writers drew on OT texts and then misapplied them (as JWs do) to events that were happening in their time.
For example, in Matthew 2, Herod commands the slaughter of all male boys 2 years old and younger. The author then says that this event was in fulfillment of the words of Jeremiah, which read, "A voice was heard in Ramah, weeping and great mourning, Rachel weeping for her children; and she refused to be comforted, because they were no more." Here Jeremiah 31:15 is being quoted. However if you go to the actual verse in Jeremiah, and read the entire chapter, you will find that the context is different. Chapters 30 and 31 of Jeremiah are a song in which restoration and a delivery from captivity is promised for the people of Israel. The only "prophecy" is that the Israelites will be restored to their homeland. The very next verse (v. 16) reads, "Thus says the LORD, Restrain your voice from weeping, And your eyes from tears; For 'your work will be rewarded,' declares the LORD, And your children will return to their own territory."
When we consider the verse in the original context, it becomes clear that the "children" spoken of are the Israelites themselves. There is absolutely nothing in the original context that hints that this verse has some sort of broader application, certainly nothing that indicates it refers to a literal slaughter of children hundreds of years in the future.
I feel the same way about Isaiah chapter 7. Before deciding whether there is prophetic reference to Jesus or not, it's best to read the entire chapter and ask yourself "What's really being said here?"
To summarize, two kings named Rezin and Pekah have waged war against Jerusalem. God tells Ahaz the king of Israel that he should not be worried; that those two kings will not overthrow Jerusalem. God then permits Ahaz to ask for sign, so that he will know for sure these things will come true. Ahaz refuses, but God provides one anyway:
"Behold, a (hebrew: alma) will be with child and bear a son, and she will call His name Immanuel. He will eat curds and honey at the time He knows enough to refuse evil and choose good. For before the boy will know enough to refuse evil and choose good, the land whose two kings you dread will be forsaken"
Notice then, that the important part of the prophecy is not the birth of the child itself, but rather the short time that would pass before the two invading kings were overthrown. I'm no expert on child psychology, but a child can distinguish between good and evil at....2 years? 3 years? In any event, this is basic thrust of the prophecy: "In just a few years these kings will no longer trouble you."
If you read just verse 14 of this chapter (with the hebrew word alma translated as "virgin"), then I can see how that looks like a strong link to the story of Jesus. But when you understand the events that prompted this prophecy and then read about the child eating "curds" and "honey" and two kings being "forsaken" then the parallel starts to fall apart.