What is the legal status regarding the sale of an 'Umm Walad' (a female slave who has borne her master's child)?

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If a master sells his Umm Walad, and she does not die before emancipation or before he frees her, she is freed upon his death if he has no heir other than her child. If he has other heirs besides her child, the value of her freedom is calculated against her child's inheritance share, and she is freed to that extent. If her value exceeds the remaining inheritance, only the portion corresponding to his share is freed, and the remainder remains enslaved to the other heirs. An exception exists according to one opinion stating that if she inherits a share from someone who would emancipate her, the emancipation extends to her entire being. If she has no child by her master, she is inherited like any other of his slaves.