I heard an explanation for why Catholics believe in the Immaculate Conception, meaning that we believe that Mary was conceived without Original Sin. Mary actually told the children one time when she appeared in Lourdes or Fatima that she was the Immaculate Conception. However, after many years of discussion in the early years of the Catholic Church, the Church Fathers came to the conclusion that there is no way that Jesus would have been born to a woman who had the original sin. Simply because Jesus grew inside of her using her blood, etc. to develop as a normal little child. It’s harder to explain then when I heard it, but this is basically it. Jesus is God and man, as man he developed in Mary’s womb with Mary’s blood, etc and there is no way God would have allowed that to happen in a woman with Original Sin. I am sure there are other reasons also, but that seems to me to make a lot of sense.
Happy, Holy, New Year