Chromosomal anomalies

Author: Elena Puscasiu, M.D. (see Authors page)

Revised: 19 April 2016, last major update February 2016

Copyright: (c) 2002-2016,, Inc.

PubMed Search: Chromosomal anomalies [title] pediatric

Related: Trisomy 13, Trisomy 18, Trisomy 21
Cite this page: Chromosomal anomalies. website. Accessed November 21st, 2018.
Definition / general
  • Chromosomal abnormalities represent the largest cause of conceptual loss
  • 6% of stillborns and 0.5% of liveborn infants have chromosomal abnormalities
  • Most embryos with chromosomal defects stop developing at ~4 weeks and abort spontaneously at 7 - 8 weeks
  • For abortuses that have reached a 2 week stage of development, the rate of chromosomal abnormalities is 78%; at 20 weeks, the rate is 62%
  • A high percentage (52%) of the chromosomal defects in the spontaneous abortion are autosomal trisomies
  • ~25% of liveborn infants with chromosomal abnormalities have autosomal trisomies, and ~40% have structural chromosomal defects
  • Trisomy 16 is the most common lethal trisomy