Leviticus 12:
6 " 'When the days of her purification for a son or daughter are over, she is to bring to the priest at the entrance to the Tent of Meeting a year-old lamb for a burnt offering and a young pigeon or a dove for a sin offering. 7 He shall offer them before the LORD to make atonement for her, and then she will be ceremonially clean from her flow of blood.
" 'These are the regulations for the woman who gives birth to a boy or a girl. 8 If she cannot afford a lamb, she is to bring two doves or two young pigeons, one for a burnt offering and the other for a sin offering. In this way the priest will make atonement for her, and she will be clean.' "
Cordially,
That Mary followed the Law in this respect is no admission of guilt. (For that matter, no woman was "guilty" of the "sin" of bearing children, especially given the charge to "go forth and multiply.")
SD