God could have entered into the world as Jesus by any number of ways, including appearing as a grown adult Jesus or as an infant via a miracle, but instead God chose to impregnate Mary through her ear (Catholics say) and dwell in her uterus for 9 full months.
Not too long before this, when Moses received the 5 books of the Old Testament and the Commandments, some written in the hand of God using his own words, containing a number of passages outlining laws equating the touching of a menstruating woman with touching the dead, something forbidden to the Jewish tribe who are rabbis. Pages are devoted to procedures on how one can disinfect and un-curse oneself after such contact. After painstakingly explaining to the Jews about the uncleanliness and dangers of even touching a menstruating woman, why is God immediately jumping into Mary's uterus and dwells within this most unholy (as described by God) location , and for 9 months (while taking only 7 days to create the universe and all within it).
Question: If a woman is a vessel of sin whose presence can desecrate a whole ritual due to her menstrual uncleanliness, and whose mangy hands are no better than a corpses (God's words in 3rd book I think) and contact with her should be avoided at all costs, why did God decide to spend around 270 days right at the very epicenter of menstrual activity as baby Jesus and come into the world in the same blood and liquids that priests can't be near to before sacrifice or otherwise that sacrifice would be rejected by God as unclean and foul?
Summarize: (Why reject offering from hands of a priest touched by a menstruating woman as blasphemous, polluted and unclean when it seems God enjoys going for lengthy 'swims' in the very same polluted "waters"for months at a time.)
Edit: Pregnant through the ear: Mary becomes pregnant when the angel Gabriel comes and announces it to her- therefore her pregnancy must have something to do with the faculty of hearing. In the early church, the breath of the Holy Ghost was supposed to have entered her ear- this was actually held to be true by many of the church Fathers, including Pope Felix. Mystics who have written on the subject include St Augustine and St Agoband- and Bernard of Clairvaux. (written by Karen on http://www.surlalunefairytales.com/boardarchives/2001/sep2001/ears.html ) but you can Google and see other sources.