According to the Torah (the first five books of the Jewish Tanakh and the Christian Bible), If a woman is engaged to man and has sex with another man prior to the wedding, both the man and woman should be put to death.

This makes things a bit tricky considering God came up with the plan of having an engaged carry the messiah to term in a culture that takes his law pretty seriously. I wonder which angel was tasked with doing a risk analysis of this plan.