Majority (50%) of early miscarriges are due to chromosomal abnormalities in the conceptus. Autosomal trisomy is the commonest cytogenetic abnormality. The most common trisomy is trisomy 16. Polyploidy is seen in 22% of abouses and monosomy constitutes 20% of abouses. Ref: Textbook of Obstetrics By D.C.Dutta, 6th Edition, Page 160