Kommentar zu Bekhorot 8:2

יוצא דופן והבא אחריו – [the second one] through the womb. As for example, that they tore the woman when twins were in her stomach, and after that they removed the first of them through the wall (i.e., by means of Caesarean section, the second left [the womb] through the womb. But to remove an offspring from the woman through the wall [i.e., via Caesarean section] and when the woman would heal, she would once again become pregnant and give birth [naturally]. Maimonides wrote that this is impossible.

Introduction Our mishnah deals with matters relating to a child born of a caesarean section, called in Hebrew one who goes out from the wall.

שניהם אינן בכור – the first [child born] is not a firstborn for [a double-portion of the] inheritance, for we require (Deuteronomy 21:15): “[If a man has two wives, one loved and the other unloved,] and both the loved and the unloved have born him sons, [but the first-born is the son of the unloved one].” The second is also not the first-born, for we require (Deuteronomy 21:17): “the first fruit of his vigor.” And the first born for a Kohen – the first is not, for we require (Numbers 18:15): “the first issue of the womb.” And the second [child born] is also not the first born for the Kohen [to be redeemed with five Selaim], for [the child] is the first-born of the womb and not the first born for offspring as for example, this one that was the offspring prior to this is not a firstborn.

A fetus extracted by means of a caesarean section and one that follows neither is a first-born for inheritance or a first-born to be redeemed from a priest. According to the first opinion, a child born through a c-section does not count as a first born because he wasn’t actually “born.” He doesn’t inherit, nor does he need to be redeemed because he didn’t open his mother’s womb. However, the next child doesn’t count as the first born either, because he is not his father’s first child. Also, even if the mother survives the c-section and has another child, it is not considered the first-born for redemption, because his mother already had a viable child, even though it didn’t “open her womb.” We should note that in mishnaic times, it would have been exceedingly rare for a woman to survive a c-section. Nevertheless, the mishnah accounts for the possibility.

רבי שמעון אומר הרשון לנחלה – he holds that (Deuteronomy 21:15) “have born [him sons],” that even for that comes out from the wall (i.e., Caesarean section) is implied.

Rabbi Shimon says: the first is a first-born for inheritance and the second is a first-born as regards [the redemption] with five selas. Rabbi Shimon disagrees completely. The first child, born of a c-section, counts as the first for inheritance, because it is its father’s first born. The second child needs to be redeemed because it “opens its mother’s womb.” It must be redeemed from the priest for five selas, which are equivalent to the five shekels mentioned in the Torah.

והשני לחמש סלעים – he holds, [that child] is the firstborn for the womb, even though he is not the first-born for offspring which is a firstborn. But the Halakha is not according to Rabbi Shimon.