It’s a very badly written story used to attempt to fullfill prophecy and embrace current cultural norms about the concept of virginity(divine, pure). It was written after the fact. Mary like all human females, had sex and gave birth.
It’s a story, used to represent meaning, not something you have to take as an historical fact.
Either that, or God would confuse humanity, by allowing previous mythical stories that talked about virgin births(in other religions) to exist, THEN claim this was the only true actual virgin birth, then present humanity with the uncomfortable notion of a sperm and an egg(which they didn’t know about back then), and then expect us all to figure it out, or be unfaithful if we sat there and thought about it for a moment.
Yeah…it’s a story, written to describe the divinity of a man that people called the christ. Don’t take it as an historical fact.