Some Hebrew translations actually render "Virgin Conception" rather than "Virgin Birth." I say, that is far more probable, as virgin conception is not an uncommon occurrence.
Did Miryam (Mary) and Joseph have full intercourse prior to their marriage? Absolutely, as it was not an uncommon practice in those days for engaged couples, because in those days the only difference between a promised marriage and actual marriage was permanent "Cohabitation." Joseph and Miryam (Mary) were not only married in their own opinion, but also, in YHVH's opinion; They loved each other with a Holy Spirit of Love, and they eventually cohabitated as a married couple. Therefore, they did not sin, and their relationship remained righteous.
Additionally, Joseph had to be the true physical father (sire) of Messiah Yahshua in order for the verses of Matthew 1:1-15 to have any TRUE purpose in being mentioned at all. We already know from research that Christianity has lied about the identity of The Holy Spirit (a mental attitude of Seeking Righteousness), so it only makes sense that they lied about this too, since the Holy Spirit is involved in Miryam's (Mary's) decision to get pregnant. The Universal Roman church actually wants mankind to believe in The Pagan Trinity. Only pagans believe that humans and gods or demigods have children from sex or a magical implantation of the seed of Abraham. This pagan concept is pure rubbish based on superstition and ignorance. Why would YHWH pervert his own promise to Abraham with a scam or misrepresentation when He didn't need to. Joseph was right there, and Miryam (Mary) was already his by promise. Would Righteous YHWH perform such an unrighteous act against both Miryam and Joseph? Absolutely Not!
YHWH limits His own power to that of pure righteousness. YHWH never deals in unrighteousness, even if He has the power to do so! Furthermore, YHWH is not an unrighteous hypocrite. Why would YHWH tell us not to follow the way of The heathen (pagans), and then turn around and do so Himself ? The Virgin Birth began with The Babylonians, Assyrians, Mesopotamians, etc. long before the normal physical birth of Messiah.