Sayyiduna Abu Ayyub al-Ansari (may Allah be pleased with him) reports this saying of the Prophet (peace and blessings be upon him): "For the young in the womb (of an animal), the slaughter of its mother counts as its slaughter."
Al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains Muhammad bin Abi Layla, who had a poor memory, but he is thiqah (trustworthy).