
The Mishna explains at what stage a delivery is considered a birth (even for a stillborn animal) to determine whether it exempts subsequent offspring from firstborn status, particularly in the case of a difficult birth where the fetus is extracted in pieces.
Rav Huna and Raba disagree regarding when the majority of the animal emerges: does the sanctity of the firstborn apply retroactively or only from that moment onward? The Gemara presents two cases demonstrating the practical ramifications of this dispute. A difficulty is raised against Rav Huna's position from our Mishna, but it is ultimately resolved through a reinterpretation of the Mishna.
A series of unanswered questions are then raised regarding whether a newborn is considered a firstborn if there is some type of chatzitza (interposition) between the fetus and the womb.
The Mishna explains that touching a dead fetus while it is in utero does not convey the impurity of a carcass. However, the Rabbis and Rabbi Yosi haGelili debate whether this exemption applies to all animals - both kosher and non-kosher- or only to kosher animals, and the Gemara presents explanations for each position.