סימן יד – דין עבר במעי בהמה
The law regarding a fetus in the belly of the mother
א
הַמַּקְשָׁה לֵילֵד וְהוֹצִיא הָעֻבָּר אֶת רֹאשׁוֹ, אַף עַל פִּי שֶׁהֶחֱזִירוֹ, הֲרֵי הוּא כְּיָלוּד וְאֵינוֹ נִתָּר בִּשְׁחִיטַת אִמּוֹ; לְפִיכָךְ, אִם הוּא בֶּן ח’ חַי אוֹ מֵת, אוֹ בֶּן ט’ מֵת, אָסוּר; וְאִם הוּא בֶּן ט’ חַי, נִתָּר בִּשְׁחִיטַת עַצְמוֹ.
Seif 1
An animal (that we are slaughtering) that happens to be in the process of giving birth, (and) if the the head (of the fetus) protrudes then returns, it is like it is born (and as if it exited its mother) and is not kosher to eat by virtue of the mother’s slaughter.
Therefore, if it in 8th month of pregnancy whether alive or dead, or in 9th month it is forbidden; if it is in 9th month and alive, it is kosher by its own slaughter.