As readers, it may be helpful to remember that the Lord is dealing with ritual purity. That which was ceremonially clean was free to participate in the ritual in the sanctuary. That which was ceremonially unclean had to be purified. Women were not alone in being classified as ceremonially unclean because of their menstrual cycle and childbirth. Men were also frequently classified as ceremonially unclean due to their discharges and diseases. The point is that the sanctuary was a place where the presence of the glory of God was manifest among his people, therefore nothing common, unclean, diseased, or foreign could enter the sanctuary. This was one of God's ways of teaching Israel about barriers between his holy nature and what was too physical and earthy, diseased or defiled.
2 Parle aux enfants d'Israël, et dis: Lorsqu'une femme deviendra enceinte, et qu'elle enfantera un fils, elle sera impure pendant sept jours; elle sera impure comme au temps de son indisposition menstruelle.