Musannaf Ibn Abi Shayba 13:677

Abu Bakr narrated to us, he said: Abda ibn Sulayman narrated to us, from Abd al-Malik, from Ata, regarding a woman who emancipated her slave girl [to be effective] after her death (tadbir): If she gives birth to children after that, they are in the same status as their mother; when she is emancipated, they are emancipated.