If an animal was pregnant and was slaughtered, the ubar (fetus) would not require its own shechita (ritual slaughter), but because it is part of its mother at that moment, it becomes kosher (fit to eat) and is permitted to eat, with no shechita.
Here we’ll talk about a case where the fetus partly came out or was cut off before the mother was slaughtered. The Mishnah says that if an animal was having a very difficult time giving birth, the fetus stuck its leg out of the womb and then pulled it back in, and then the mother was slaughtered, the fetus is permitted to eat, even though the leg went out before the shechita. The fetus is considered unborn and therefore part of the mother. When shechita is performed on the mother, the fetus becomes permitted as well. But the leg is forbidden. Even though it returned to the womb before shechita, we say it is forbidden. We learn this from the pasuk (verse). The peshat (plain meaning) of the pasuk—that meat torn in the field is to be eaten—is talking about meat or an animal that was attacked by a wild animal, and therefore is just a terefa, torn up. So that’s the peshat. But we learn from there that any meat that is in the field—that means meat that has left its normal enclosure—which in our case is meat that has left the womb, cannot go back in, in terms of having the mother’s shechita permit it. The limb becomes forbidden, just like a normal terefa. Just like a terefa, once it is torn, it has no recourse; it can never become permitted. The same thing applies here. A limb cannot become permitted with the mother’s shechita, even if it goes back into the womb before shechita. Once it leaves, the mother’s shechita cannot allow it. If it fully left and therefore can get its own shechita, that would be okay. But the mother’s shechita could never permit it once it leaves the body.
If the fetus stuck its head out of the womb, even though it pulled it back in and went back into the mother’s stomach, the fetus is considered to be born and no longer part of the mother. Therefore, the whole fetus, even the part that never left the womb, would not be permitted through the mother’s shechita. The fetus is born and is looked at as its own animal. If it is found dead inside, it is a nevela (carcass of an unslaughtered animal). If it comes out alive, then you’re allowed to do shechita on it, and it could be eaten.
If someone sticks their hand inside the mother and cuts off part of a fetus that is in her womb, leaving the cut part inside, the cut part becomes permitted to eat with the mother’s shechita. If someone makes a cut in the mother and cuts off part of the mother’s spleen or kidneys, leaving them inside her, they are forbidden to eat, even though they were inside her when she was slaughtered. This is the general rule: anything inside her that is part of her actual body, like the kidneys we just mentioned, remains forbidden after it is cut off, even after the shechita. Something inside her that is not part of her actual body, but is part of the fetus, is permitted with the shechita.
We learn this from the pasuk, where it says, “Anything that’s in the animal, anything inside of it is to be eaten.” We learn now that when an animal is slaughtered, you could eat anything separate that is in the animal, but only when the animal is otah, which means, “It, it’s complete.” When we say “in the animal,” we’re talking about something that doesn’t take away from the completeness of the animal. But when we say “in the animal,” we’re talking about something that was cut from the animal and takes away from its perfectness or completeness; then it’s a problem, and it can’t be eaten. So only something that is separate from it, that is not part of it but is inside it, becomes permitted with shechita.