ULTRASOUND NT/NB

The NT/NB ultrasound (Nuchal Translucency/Nasal Bone ultrasound) is a prenatal screening test typically performed during the first trimester of pregnancy, between 11 and 14 weeks gestation. It helps assess the risk of chromosomal abnormalities, such as Down syndrome (Trisomy 21), Trisomy 18, and other genetic conditions.

What is Measured?

1. Nuchal Translucency (NT):

   • NT refers to the fluid-filled space at the back of the baby's neck.
   • An increased NT measurement may indicate a higher risk of chromosomal abnormalities or congenital heart defects.
   • The normal range is usually less than 3.5 mm, but this varies with gestational age.

2. Nasal Bone (NB):

   • The presence or absence of the nasal bone is assessed.
   • Absence or underdevelopment of the nasal bone is associated with chromosomal abnormalities like Down syndrome.

How the Test is Done:

• Preparation: No special preparation is needed, but having a full bladder may improve imaging clarity.
• Procedure:
  1. Conducted via abdominal ultrasound or, in some cases, transvaginal ultrasound.
  2. The sonographer measures the NT and examines the nasal bone while assessing other fetal features.

Why It’s Important:

1. Risk Assessment: Combines NT/NB measurements with maternal blood tests (PAPP-A and beta-hCG) to calculate the risk of chromosomal abnormalities.
2. Early Detection: Identifies pregnancies requiring further diagnostic tests, such as amniocentesis or chorionic villus sampling (CVS).
3. Heart Defects: An increased NT measurement can also indicate a higher risk of congenital heart abnormalities.