Sayyiduna Ka'b bin Malik (may Allah be pleased with him) reports from the Prophet (peace and blessings be upon him) that, regarding the slaughter of the young in the womb of an animal, he said that the slaughter of its mother counts as its slaughter.
Al-Tabarani recorded it in al-Mu'jam al-Kabir and al-Mu'jam al-Awsat; its chain contains Isma'il bin Muslim, who is da'if (weak).