Some of the narrative in the gospels is concerned with fulfilling the prophesies of Isaiah, since that would build a case for Jesus being the Messiah, which was something people were interested in at the time.
Isaiah didn’t clearly prophesy a virgin birth, but the writers of Matthew and Luke were probably working from the Septuagint, a greek [mis-]translation which turns the prophecy into one of a virgin birth. So, thinking that a virgin birth was required, they wrote it into the story.
The question of whether someone claiming to be made pregnant by God is making a plausible claim, is fairly moot when the whole episode was probably made up anyway.
Some of the narrative in the gospels is concerned with fulfilling the prophesies of Isaiah, since that would build a case for Jesus being the Messiah, which was something people were interested in at the time.
Isaiah didn’t clearly prophesy a virgin birth, but the writers of Matthew and Luke were probably working from the Septuagint, a greek [mis-]translation which turns the prophecy into one of a virgin birth. So, thinking that a virgin birth was required, they wrote it into the story.
The question of whether someone claiming to be made pregnant by God is making a plausible claim, is fairly moot when the whole episode was probably made up anyway.