Gynaecology & Obstetrics General obstetrics efe75e02 Most common cause of the first-trimester aboion is A Chromosomal anomalies B Infections C Rh incompatibilty D Cervical incompetence High-Yield Explanation Causes of 1st trimester aboion : Genetic factors -50% Endocrine disorders Immunological disorders Infection Unexplained Ref: Dutta Obs 9e pg 153.