1. The Beraisa discusses the case of a woman who had birth pains along with bleeding for three days, and then had a caesarean section.
2. Ravina explains the next case in this Beraisa (see #1) regarding whether the blood that comes out is Tamei.
3. Rav Yosef explains this case (see #1) differently.
4. Rebbi Yochanan: Everyone agrees that blood that exits abnormally (i.e. via caesarean section) does not make a woman a Nidah.
5. Reish Lakish: If part of the womb falls out of a woman, she is Tamei.
A BIT MORE
1. Tana Kama: She is considered a Yoledes b'Zov. Rebbi Shimon: She is not considered a Yoledes b'Zov.
2. Ravina understands that the case is where the blood exited normally, as opposed to the child. The Tana Kama: it is not a birth, and there is Dam Zivah which makes her Tamei. Rebbi Shimon: it is a birth, and the blood is only blood from the birth which does not make her Tamei.
3. Rav Yosef understands that the case is where the blood also exited via caesarean section. The argument is whether blood that comes out of the womb -- but does not exit normally -- causes Tum'ah to one who touches it.
4. Reish Lakish argues that if one maintains that the blood in the womb is Tamei even when it exits abnormally, it also causes the woman to be a Nidah.
5. The Gemara concludes that she is Tamei because the womb touched her, and not that it causes her to be a Nidah.