We asked the Messenger of Allah (may Allah's peace and blessings be upon him) about the fetus (of edible animals). He said: Eat it if you wish, for it is considered legally slaughtered with the slaughtering of its mother
Authentic hadithعن أبي سعيد قال: سألْنا رسول الله صلى الله عليه وسلم عن الجَنِينِ فقال: «كُلُوهُ إنْ شِئْتُم، فإنَّ ذَكاتَه، ذَكاةُ أُمِّهِ».
Abu Sa‘īd reported: We asked the Messenger of Allah (may Allah's peace and blessings be upon him) about the fetus (of edible animals). He said: "Eat it if you wish, for it is considered legally slaughtered with the slaughtering of its mother."
Explanation
The fetus of a slaughtered animal, if taken out dead, is lawful to eat. The slaughtering of the mother is enough to make it lawful to eat, for the fetus was part of the animal when it was slaughtered. Being so, the parts of the animals do not require independent slaughtering.
Source · Narrated by Ibn Majah - Narrated by At-Termedhy - Narrated by Abu Daoud - Narrated by Ahmad
From the Hadith Encyclopedia (hadeethenc.com).