Parshat Tazria begins by setting out the rules which govern a woman upon giving birth. In order to regain a status of ritual purity and what I would call “normalcy”. She must undergo a time-related sanctification process. This process varies in length depending on whether she has given birth to a boy or a girl. It is 41 days for a male child and 81 days for a baby girl.
The question for me is why is additional time required when the mother has given birth to a girl?
I think it goes like this: During the period of gestation there is a presumption that the mother knows or thinks she knows that she is carrying a girl. At that point the mother realizes that it is incumbent upon her to pass on the superior wisdom and understanding, spirituality, sensitivity and teaching skills inherent in a woman to her unborn daughter.
She does this having in mind that one day the unborn daughter will have children of her own and likewise have the responsibility to educate them. Passing on this bounty to her unborn daughter depletes the mother of her natural gifts, and she needs more time to spiritually recover and resume her maternal responsibilities.