The gospel lesson for the fourth Sunday of Advent (Matthew 1:18-25) tells us of Joseph's implication in the birth of Jesus. Matthew's gospel shows an appreciation for the role of the male in that culture, who normally would not get intangled in birth matters.
The text says, "he took her as his wife, but had no marital relations with her until she had borne a son; and he named him Jesus." I think that didn't just mean sexual relations. In that culture, with extended families involved and the strong distinctions between male and female roles, Joseph perhaps had little contact with Mary until after the birth.
I know this idea runs contra to the idyllic picture of Joseph by Mary's side as she gives birth in the manger. But that image is mainly our projection back on to the first century culture. A Jewish male would have nothing to do with birthing. For them, not only would it violate the codes of gender roles, it was unclean, literally and ceremonially.
The beautifully done movie, The Nativity, has it wrong. It shows Joseph assisting (receiving the baby as it emerges). This is after Joseph can find no one to help. For other reasons, which I won't go into here, I don't think that's what Luke intends at all when he tells us there was no room for them in the inn.
If the little town was full of people for the census, there would have been women to come to the aid of Mary. And they would have done so, honoring the bond of women and the codes of Mideastern hospitality. Once the child had been born, a messenger would have been sent to find the father and announce the news of the birth.
I enjoy reading the work of John Pilch, who has devoted his life to the study of social behaviors and cultural norms of the Bible. So I'm sure he gets credit for many of my thoughts on this, but I'm not exactly sure what is his (and where I read it) and what I've added with my own study. But this much I do remember reading from Pilch: if baby born was a male, the messenger would joyfully announce the "good news" to the father. (If it was a girl, the messenger would try to soften the bad news with a remark like, "Perhaps the father will receive a handsome dowry for his new child.")
The messenger bearing good news plays prominently in Luke's account. Luke takes this common behavior and changes it for a very Lukan emphasis, that Jesus is the redeemer of the whole world. Instead of recording the messenger going to tell Joseph of the birth, an angelic messenger goes to the shepherds to announce "I bring you good news of great joy to all people, for unto you is born this day in the city of David, a Savior, who is the Messiah, the Lord."
But back to Matthew, who tells us Joseph "is a righteous man," one who honors not just the letter of the law, but the spirit of the law as well. This Joseph "took her as his wife," staking his honor and his future on the promise of God. Who takes the greater risk? God, trusting Joseph will believe, or Joseph, trusting God will fulfill?