Niddah 10:5

If a woman died and a reviis of blood came out from her, it transmits ritual impurity as a bloodstain and through overshadowing; Rabbi Yehuda says it doesn’t transmit impurity as a bloodstain because it detached from her after she died. He agrees, however, that if she died mid-labor and a reviis of blood came out from her, then it transmits ritual impurity as a bloodstain (because it detached while she was still alive). Rabbi Yosi said this is why it doesn’t transmit impurity through overshadowing (i.e., because it’s not part of a corpse).

Niddah 10:6

Originally, the Sages said that a woman following childbirth, in the time of pure blood, would pour water to wash the Pesach offering. Later, they said that when it comes to sanctified items, she’s like a person who touched someone who was rendered impure by a corpse. That’s the opinion of Beis Hillel; Beis Shammai say that she’s even like the one who was rendered impure by a corpse.