Are you still not getting it? The Immaculate Conception is about Jesus Christ — have an immaculate womb for him.
I get it that that is what you are told to believe and to justify the unscriptural dogma, but it doesn't mean it is true. What is an "immaculate womb" anyway? According to Scripture, Mary was a virgin, she had never had sex with anyone, so her womb was inviolate, pure. That doesn't automatically have to mean she was a sinless human from birth. The miraculous part is that a virgin would conceive and bear a son. THAT was the prophecy. Nothing was ever said that this virgin would have to be free from all sin - such a person could not have existed because all mankind is under the sin of the first man, Adam. The miracle was Christ was God in the flesh. He was sinless because he is God, not because his mother was a normal human being. THAT is about Jesus.
Wombs are incapable of sinning. One womb is as immaculate spiritally as another. Sin is not spread through the bloodstream like HIV or Hep C.
And I just came from a play that reminded me that God let His son be born in a filthy sheep pen, and announced the wonderful news first to a bunch of ragged, stinky, sinful shepherds who were the first to greet him, after of course His sinful step-father, who probably delivered him with his dirty hands.
Seems to me that if He wanted Jesus to be insulated against sin he would have had Mary be a incredibly rich recluse locked in a luxurious tower with him for his first 30 years.