This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
Which of the following is the most common cause of first trimester aboion? 
Select and explain. 
A. Syphilis, B. Chromosomal abnormalities, C. Rhesus isoimmunization, D. Cervical incompetence
B: Chromosomal abnormalities
Answer: B: Chromosomal abnormalities 
Explanation: 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