Recurrence of trisomy: implications for screening

18 May 2005

Trisomy is a condition in which a fertilised egg contains three copies of a particular chromosome rather than the normal two copies, producing a total of 47 chromosomes in the cell. For most chromosomes, the presence of an additional copy is lethal and embryos will not develop properly, leading to pregnancy loss. Some forms of trisomy may permit embryonic development and even live births; the

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