This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abortion, Subject name: Gynaecology & Obstetrics
Commonest cause of first trimester abortion is: 
Select and explain. 
A. Monosomy, B. Trisomy, C. Triploidy, D. Aneuploidy
D: Aneuploidy
Answer: D: Aneuploidy 
Explanation: Ans. is d, i.e. AneuploidyRef. Williams 24/e, p 351The M/C cause of early miscarriages is aneuploidy (i.e. chromosomal anomaly).Amongst the aneuploid abortions--autosomal trisomy is the most frequently identified chromosomal anomaly.Trisomies have been identified in abortuses for all except chromosomal number 1 and those with 16, 13, 18, 21 and 22 are most common.The single most specific chromosomal abnormality in abortions is Monosomy X (45X).As a have discussed Best answer for M/C cause of 1st trimester abortion--Aneuploidy > Trisomy > Monosomy X > Trisomy 16.