<prompt> Commonest cause of first trimester miscarriage is:SyphilisCervical incompetenceChromosomal abnormalitiesRhesus isoimmunisation  <response>: Ans. c Chromosomal abnormalitiesDutta 6th160With respect to first trimester abortions, 75 of the abortions take place before 16thweek and out of these, about 75 occur before the 8thweek of pregnancy. Chromosomal abnormality in the conceptus is the commonest cause of miscarriage. Autosomal trisomy particularly Trisomy 16 is the commonest cause for spontaneous abortion. 