However, it is held in Mormonism that this was how Jesus was conceived, one among many reasons why the enormous popularity of the Mormons within American religion - numerically third only to the Catholics and to the Southern Baptists, and the clear direct or indirect originators of numerous ideas such as "Manifest Destiny" - raises very serious questions about whether the American Republic, as such, is any sort of bulwark of Christianity. Not unanswerable questions. But very serious ones.
Both Jews and pagans made all sorts of contrary claims, but one was completely unknown to either, namely that Jesus had been the natural child of Mary and Joseph. No such suggestion was ever made by anyone in the first eighteen centuries of Christianity's existence. Even the Qur'an has the "Prophet Isa" born of the "Virgin Mariam". Apart from that partial retelling in the Qur'an, the Biblical account is unique, and could not be less like any of the parallels that are routinely alleged.
That Islam - a Semitic reaction against the recapitulation in Christ and His Church of all three of the Old Israel, Hellenism, and the Roman Empire - depicts Jesus as both virgin-born and the Messiah foretold by the Hebrew prophets is an important insight into the debate as to whether or not the circumstances of His conception described in the New Testament really are the fulfilment of Old Testament prophecy.
Of course, had there been no expectation that the Messiah would be virgin-born, then there would have been no reason for the Evangelists to invent it. And that would have been just as strong an argument in the doctrine's favour. But the Islamic view, staunchly Semitic and anti-Hellenistic as it is, adds considerable weight to the belief that the Virgin Birth is, as the New Testament writers maintain entirely matter-of-factly that it is, the fulfilment of the words of the Old Testament prophets.
It is often contended that it is not clear that the prophecy in Isaiah actually refers to a virgin. Well, it certainly does in the Septuagint, and, contrary to what used to be asserted, first century Palestine is now acknowledged to have been profoundly Hellenised. So either the Septuagint prophecy is indeed being fulfilled explicitly, or else there was no expectation that the Messiah would be virgin-born, and thus no reason to make up that Jesus had been. The doctrine works either way.