Yahya related to me from Malik from Nafi that Abdullah ibn Umarsaid, "When a she-camel is slaughtered, what is in its womb isincluded in the slaughter if it is perfectly formed and its hair hasbegun to grow. If it comes out of its mother's womb, it is slaughteredso that blood flows from its heart."
USC-MSA web (English) reference: Book 24, Hadith 8
Arabic reference: Book 24, Hadith 1053