Human medical cytogenetics:
Chromosomal syndromes in spontaneous abortions & live births

    At least 15% of all human conceptuses are aborted spontaneously in the first trimester. Half of these have detectable cytogenetic anomalies. About 0.6% of live births exhibit one of a variety of recognized cytogenetic syndromes. The most common are Klinefelter Syndrome (XYY males: 28% of total), Down Syndrome (trisomy of Chromosome 21: 20% of total), and Turner Syndrome (monosomy of the X chromosome in women: 8% of total). Note that a large fraction of  conceptuses with Trisomy 21 and XO are aborted spontaneously. The figure is based on data from Sankaranarayanan (1979) ; current research and earlier detection suggests that >30% of conceptuses are aborted spontaneously.

    Note on Names: The three syndromes mentioned are named after the physicians who first described them. Current practice recognizes that John Langdon Down neither had the syndrome nor owned it. It is thus incorrect to call it "Down's Syndrome" and the accepted term is "Down Syndrome": The same principal applies to other medical conditions.

Figure ©2002 by Griffiths et al.; all text material ©2014 by Steven M. Carr