Increased nuchal translucency with normal karyotype

Am J Obstet Gynecol. 2005 Apr;192(4):1005-21. doi: 10.1016/j.ajog.2004.12.093.


Increased fetal nuchal translucency (NT) thickness between 11 and 14 weeks' gestation is a common phenotypic expression of chromosomal abnormalities, including trisomy 21. However, even in the absence of aneuploidy, nuchal thickening is clinically relevant because it is associated with an increase in adverse perinatal outcome caused by a variety of fetal malformations, dysplasias, deformations, dysruptions, and genetic syndromes. Once the presence of aneuploidy is ruled out, the risk of perinatal outcome dose not statistically increase until the nuchal translucency measurement reaches 3.5 mm or more (>99th percentile). This increase in risk occurs in an exponential fashion as the NT measurement increases. However, if the fetus survives until midgestation, and if a targeted ultrasound at 20 to 22 weeks fails to reveal any abnormalities, the risk of an adverse perinatal outcome and postnatal developmental delay is not statistically increased.

Publication types

  • Review

MeSH terms

  • Chromosome Disorders / diagnosis*
  • Congenital Abnormalities / epidemiology
  • Congenital Abnormalities / genetics*
  • Crown-Rump Length
  • Developmental Disabilities / diagnosis*
  • Developmental Disabilities / epidemiology
  • Female
  • Fetal Death
  • Fetal Diseases / diagnostic imaging
  • Fetal Diseases / genetics*
  • Follow-Up Studies
  • Humans
  • Incidence
  • Infant, Newborn
  • Karyotyping
  • Male
  • Nuchal Translucency Measurement*
  • Pregnancy
  • Pregnancy Trimester, First
  • Risk Assessment
  • Ultrasonography, Prenatal