Aneuploidy, is the most common genetic abnormality, accounting for up to 50% of clinical miscarriages. All are true about aneuploidy, EXCEPT:
Also known as Edwards syndrome,trisomy 18 has an overall frequency of 1 in 8000 newborns and is three to four times more common in females. As with other aneuploidies, its incidence is much higher in the first trimester, and 85 percent of fetuses die between 10 weeks and term. Ref: Cunningham F.G., Leveno K.J., Bloom S.L., Hauth J.C., Rouse D.J., Spong C.Y. (2010). Chapter 12. Genetics. In F.G. Cunningham, K.J. Leveno, S.L. Bloom, J.C. Hauth, D.J. Rouse, C.Y. Spong (Eds), Williams Obstetrics, 23e.
30-40% of trisomy 21, fetus die between 12 weeks and 40 weeks
50-60% of trisomy 18, fetus die between 12 weeks and 40 weeks
Occurrence of triploidy has no relation with the progression of mother's age
In previous pregnancy with trisomy 21 due to non disjunction, the risk in future pregnancy is .75% higher