That Mary remained virgin both before and after the birth of Jesus is dogma of the Catholic Church. What is not dogma is under what circumstances she chose to be a virgin all of her life. Catholics believe that the NT indicates her intention of remaining virgin based on her response to the angel Gabriel "How shall this be since I do not know man?" Now if she was expressing disbelief like Zechariah did, she would have been punished like Zechariah. Was she expressing complete ingnorance of the mechanics of getting pregnant? (Unlikely in a farming community.) Or was she curious how that was going to happen since the angel knew she was vowed to be a virgin? One of the possibilities that is suggested in apocryphal works such as the Protoevegelium of James and the Gospel of the Birth of Mary, is that Mary was consecrated as a young girl to work in the temple. When she reached puberty the onset of menstruation would have introduced problems of ceremonial uncleanliness and a guardian, Joseph, was found for her. Here is an article on Catholic Answers that will get you started on references and details. The scholars on all sides are far from agreed on whether there was any such thing as a consecrated virgins in the Temple and I am not attempting to build a case for or against it. My reason for raising this idea is this…..what would the implications for Mary be, if she did spend many years working the in the Temple as a consecrated virgin? She would have been known by the priests, by those who worked in the Temple and its environs and they would have known about her vow of virginity.

Imagine then, showing up with a baby for the ritual purification after childbirth. Imagine the kind of guts it would take to show up with apparent evidence of that vow having been broken. I wonder if that's how Anna and Simeon knew that Jesus was the Messiah. They knew that the Messiah would be born to a virgin and they knew Mary would never break that vow. They had the courage to believe the impossible even when all reasonable explanations suggested a very ordinary reason for her to be carrying that baby. I'm guessing that Anna and Simeon were the exceptions and I wonder if she went home a cried at the end of the day.