It is mentioned in the book of Leveticus, Ch. No.12, Verse No.1 to 5, and we know medically, that after a mother gives birth to a child, the post-partal period, it is unhygienic. To say it is 'unclean', Religiously - I have got no objection. But Leviticus, Ch. No.12 Verse No.1 to 5, says that... 'After a woman gives birth to a male child, she will be unclean for 7 days, and the period of uncleanliness will continue for 33 days more. It she give birth to a female child, she will be unclean ...