MC cause of abortion in first trimester is :

Ans. is 'a' i.e., Trisomy [Ref: Williams 24th/e p. 351* Abortion occurring without medical or mechanical means to empty the uterus is referred to as spontaneous.* More than 80% of abortions occur in the first 12 weeks of pregnancy, and at least half result from chromosomal anomalies.* After the first trimester, both the abortion rate and the incidence of chromosomal anomalies decrease.* Trisomy 16 is the most common abnormal karyotype found in the abortus.* Monosomy X (45 X), the second most frequent chromosomal abnormality (after trisomy), usually results in abortion and much less frequently in live born female infants (Turner syndrome).* Trisomies have been identified in abortus for all except chromosome 1