<prompt> Which of the following is the most common cause of first trimester aboion?SyphilisChromosomal abnormalitiesRhesus isoimmunizationCervical incompetence  <response>: 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 