Nuchal translucency measurement

Ultrasound measurement used in prenatal screening

Nuchal translucency measurement
Ultrasound image showing nuchal translucency
Synonyms	N/A
Pronounce	N/A
Specialty	Obstetrics
Symptoms	None
Complications	Chromosomal abnormalities
Onset	First trimester of pregnancy
Duration	Temporary
Types	N/A
Causes	Genetic factors
Risks	Increased risk of Down syndrome, Trisomy 18, Trisomy 13
Diagnosis	Ultrasound
Differential diagnosis	N/A
Prevention	N/A
Treatment	None (screening test)
Medication	N/A
Prognosis	N/A
Frequency	Common in prenatal care
Deaths	N/A

Nuchal translucency measurement is a prenatal screening test that involves the use of ultrasound to measure the fluid-filled space at the back of a developing fetus's neck. This measurement is typically performed between 11 and 14 weeks of gestation and is used to assess the risk of certain chromosomal abnormalities, such as Down syndrome (Trisomy 21), Trisomy 18, and Trisomy 13.

Procedure

The nuchal translucency (NT) measurement is conducted via a transabdominal ultrasound. The procedure involves the following steps:

1. The pregnant individual lies on an examination table, and a clear gel is applied to the abdomen.
2. A transducer is moved over the abdomen to obtain images of the fetus.
3. The sonographer measures the thickness of the nuchal translucency, which appears as a black, fluid-filled space at the back of the fetal neck.

The measurement is typically expressed in millimeters and is compared against gestational age-specific norms to assess risk.

Significance

An increased nuchal translucency measurement can indicate a higher risk of chromosomal abnormalities. However, it is important to note that NT measurement is a screening test, not a diagnostic test. It is often combined with other markers, such as maternal serum markers, in the first trimester combined screening test to provide a more comprehensive risk assessment.

Interpretation

The results of the NT measurement are interpreted in conjunction with other factors, including:

• Maternal age
• Gestational age
• Biochemical markers (e.g., free beta-hCG, PAPP-A)

A higher-than-normal NT measurement may prompt further diagnostic testing, such as chorionic villus sampling (CVS) or amniocentesis, to confirm the presence of chromosomal abnormalities.

Limitations

While nuchal translucency measurement is a valuable screening tool, it has limitations:

• It does not diagnose conditions but only assesses risk.
• False positives and false negatives can occur.
• The accuracy of the measurement depends on the skill of the sonographer and the quality of the ultrasound equipment.

Also see

• Prenatal screening
• Ultrasound in obstetrics
• Down syndrome
• Trisomy 18
• Trisomy 13