In plain words
Nuchal translucency is the thin space of fluid under the skin at the back of a baby's neck. It is measured by ultrasound between 11 and 14 weeks of pregnancy. Most babies have a small amount of fluid there. A larger measurement is linked to a higher chance of some chromosome conditions and heart differences. It is one part of the first-trimester screen. It is not a diagnosis. A measurement that is larger than average does not mean a baby has a condition. Most babies with a larger reading are healthy. The measurement is often combined with blood tests and the mother's age to estimate risk. Mothers may be offered more testing after a larger reading.
The deeper version
Nuchal translucency reflects subcutaneous fluid at the fetal neck, measured in the midsagittal plane with between 45 and 84 millimeters. Increased thickness is associated with , cardiac defects, and some genetic syndromes, through lymphatic and cardiac mechanisms. The Fetal Medicine Foundation combined-screening algorithm (Nicolaides, 2011) integrates nuchal translucency, maternal serum markers, and maternal age to estimate risk. Screening detection rates for trisomy 21 at a 5 percent false-positive rate are reported near 90 percent in these algorithms. Measurement quality and operator certification affect results, and has largely replaced NT as a primary screen in some settings.
Where it comes up
- Prenatal tests and ultrasounds: what each one isPregnancy: Your Body
- Pregnancy at 35 and olderPregnancy: Your Body
- Expecting twins or morePregnancy: Your Body
What mothers here say about nuchal translucency
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Sources
- Nicolaides KH — Turning the pyramid of prenatal care. Fetal Diagnosis and Therapy 2011
- American College of Obstetricians and Gynecologists — Practice Bulletin 226: Screening for fetal chromosomal abnormalities, 2020