There are more plausible explanations but I wanted to keep the whole virgin birth theme because it is more fun.
As for technology, I believe it was Arthur C. Clarke that stated that any significantly advance form of technology would be indistinguishable to magic or the supernatural. I mean, if you took a military Humvee with a .50 cal machine gun back in the days of the 1st century C.E. how do you think people would react?
Now, the most plausible explanation for Jesus' birthing, not going the whole God route, is that she got pregnant out of wedlock, a stoning offense in those days I believe, which Mary and Joseph concocted a story (or maybe it was just Mary) that would not get herself killed.