Nuchal translucency is used in
**Core Concept**
Nuchal translucency (NT) is a measurement of the thickness of the subcutaneous tissue at the back of the fetal neck, taken between 11 and 14 weeks of gestation. This parameter is used as an early marker for the risk of chromosomal abnormalities, such as Down syndrome, trisomy 18, and trisomy 13.
**Why the Correct Answer is Right**
The measurement of nuchal translucency is based on the principle that increased NT thickness is associated with an increased risk of fetal aneuploidy. This is thought to be due to the accumulation of fluid in the subcutaneous tissue, which may be a result of cardiac or other fetal anomalies. The NT measurement is usually performed using ultrasound and is often used in conjunction with other markers, such as maternal age and serum screening, to assess the risk of chromosomal abnormalities.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the measurement of nuchal translucency.
* **Option B:** While nuchal translucency is used in the assessment of fetal anomalies, it is not a direct measure of fetal weight.
* **Option C:** This option is not related to the use of nuchal translucency in obstetrics.
**Clinical Pearl / High-Yield Fact**
A nuchal translucency thickness of 3.5 mm or greater is considered to be at the 95th percentile and is associated with an increased risk of chromosomal abnormalities.
**Correct Answer: C. Nuchal translucency is used in screening for chromosomal abnormalities, such as Down syndrome.**