After a woman gives birth to a girl or miscarries a girl, she needs to wait out eighty days, and then bring a sacrifice. What happens if during this time she again conceived and then miscarried?
Beit Hillel and Beit Shammai argue specifically about a case when she miscarried on the night after eighty days has passed. Beit Shammai exempt her from a second offering. Since this was night, and no offerings are brought in the Temple at night, she could not have possibly brought her first one. Therefore, the second incident is merged with the first one, and her one offering, in which she is already obligated, suffices. Beit Hillel, on the other hand, reason that since eighty days have passed and she will be able to bring her sacrifice on the morrow, then even now she is considered in the new time period, and her miscarriage creates an obligation for a new sacrifice.
It once happened that the price of birds, usual sacrifices after childbirth, rose twenty-five times, to a golden dinar. Rabban Shimon ben Gamliel then swore by one of the seven Heavens, called “Dwelling Place,” that the price will go down to silver dinars. He promulgated a law that a woman who needs to bring multiple offerings can bring only one. One of the possible explanations for this law is that a poor woman is indeed required to bring only one offering, and under these circumstances everyone was considered poor.
Art: Charles Joseph Grips - Mother And Baby In An Interior