Majority (50%) of early miscarriage are due to chromosomal abnormality in the conceptus.
Autosomal trisomy is the commonest cytogenetic abnormality about 50%. Trisomy for
every chromosome except chromosome 1 has been reported.
Trisomy 16 is the most common trisomy in human pregnacies, occuring in more than
1% of pregnancies. Only those pregnancies in which some normal cells occur in addition
to the trisomy cells, survive. This condition usually results in spontaneous miscarriage in
the first trimester.
Structural chromosomal rearrangements are observed in 2-4% of abortuses. These includes
translocation, deletion, inversion and ring formation. Other chromosomal abnormalities
like mosaic, double trisomy etc are found in about 4% of abortuses.
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