Since the thread is open, I’ll post this link to a discussion on what the Greek text means:
“In our case all it would mean is that Mary had received favor from God in the past and was still in His good-graces. In short, this is just a verb form, not a miracle or the representation of one.”
One thing that causes me to question this doctrine of Mary having to be "sinless" from birth in order to carry the Lord Jesus in her womb is that it takes away from her the ability to freely choose to obey God. She is in essence, a robot with no free will to accept the great calling God made to her. It speaks to God's foreknowledge, of course, that He knew Mary would accept so He made her completely sinless at birth, but I think it skews the whole idea of free will. If she had said no, would she become a sinner retroactively?
I also wonder why there is no mention anywhere in Scripture of her specifically having this attribute. Surely, such a perfect person could not go unnoticed all those years, could she? Did her parents ever say anything to anyone about what a perfect, obedient child she was and all the neighbors were in awe of her and jealous of her parents? I'm not asking this to be disrespectful - I honor Mary and appreciate her role in bringing our savior into the world - but it just seems unlikely that she would not have been the talk of the town and somebody would have made it known an exemplary woman like her lived. Besides, we already know that the Greek word for sin is "hamartanÅ" which means "missing the mark" and as Romans 3:23 says, we ALL "come short of the glory of God".