Nuchal scan
| Nuchal scan | |
|---|---|
Measurements of fetal nuchal translucency, nasal bone and facial angle according to the standards of the Fetal Medicine Foundation | |
| Synonyms | Nuchal translucency |
| Purpose | Used to screen for abnormalities in a developing fetus |
A nuchal scan or nuchal translucency (NT) scan/procedure is a sonographic prenatal screening scan (ultrasound) to detect chromosomal abnormalities in a fetus, though altered extracellular matrix composition and limited lymphatic drainage can also be detected.[1]
Since chromosomal abnormalities can result in impaired cardiovascular development, a nuchal translucency scan is used as a screening, rather than diagnostic, tool for conditions such as Down syndrome, Patau syndrome, Edwards Syndrome, and non-genetic body-stalk anomaly.[2]
There are two distinct measurements: the size of the nuchal translucency and the thickness of the nuchal fold. Nuchal translucency size is typically assessed at the end of the first trimester, between 11 weeks 3 days and 13 weeks 6 days of pregnancy.[3] Nuchal fold thickness is measured towards the end of the second trimester. As nuchal translucency size increases, the chances of a chromosomal abnormality and mortality increase; 65% of the largest translucencies (>6.5mm) are due to chromosomal abnormality, while fatality is 19% at this size.[2] A nuchal scan may also help confirm both the accuracy of the pregnancy dates and the fetal viability.
- ^ Souka AP, Von Kaisenberg CS, Hyett JA, Sonek JD, Nicolaides KH (2005-04-06). "Increased nuchal translucency with normal karyotype". American Journal of Obstetrics and Gynecology. 192 (4): 1005–1021. doi:10.1016/j.ajog.2004.12.093. PMID 15846173.
- ^ a b Souka AP, Von Kaisenberg CS, Hyett JA, Sonek JD, Nicolaides KH (2005-04-06). "Increased nuchal translucency with normal karyotype". American Journal of Obstetrics and Gynecology. 192 (4): 1005–1021. doi:10.1016/j.ajog.2004.12.093. PMID 15846173.
- ^ Gomella, Tricia; Cunningham, M. (2013). Neonatology : management, procedures, on-call problems, diseases, and drugs. Gomella, Tricia Lacy, Cunningham, M. Douglas, Eyal, Fabien G. (7th ed.). New York. ISBN 9780071768016. OCLC 830349840.
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