Shulchan Arukh, Yoreh De'ah 14/שולחן ערוך·יורה דעה י״ד

2He extended his hand and retracted it (meaning before the slaughtering): what emerged from the limb outside is forbidden. But what remained inside and the place of the cut is permitted. If he did not retract it before the slaughtering, even the place of the cut is forbidden, but what is inside is permitted, even if it is a minority. Gloss: All this refers only to the matter of it being permitted by the slaughtering of its mother like any other fetus found within it. However, if the animal later gave birth, even the limb that emerged and was retracted is permitted, because its own slaughtering permits everything. This is the conclusion of the Beit Yosef and Rabbi Yosef Ibn Habib, and Kol Bo in the name of some authorities, and this is also proven by the Maharshal in Perek Behemah Hamakshah, Siman 1, and this is the implication of the poskim, and it is obvious.