Nuchal Fold
The thickness of soft tissue at the back of the fetal neck measured on ultrasound as a marker for chromosomal abnormalities.
Full Definition
The nuchal fold refers to the soft tissue thickness measured at the back of the fetal neck during second-trimester ultrasound examination. This measurement is typically taken between 15-20 weeks of gestation and differs from the first-trimester nuchal translucency measurement. An increased nuchal fold thickness (>6mm) may indicate an increased risk of chromosomal abnormalities, particularly Down syndrome. The measurement is performed in the axial plane at the level of the cerebellar hemispheres and is an important component of the second-trimester screening protocol.
Usage
Usage note: Distinguish from nuchal translucency, which is measured in the first trimester.
In Context
- "The nuchal fold measured 7.2mm, prompting genetic counseling referral." — Ultrasound report
- "Nuchal fold thickness was within normal limits at 4.1mm." — Prenatal screening documentation