What is nuchal translucency (NT), Nasal Bone (NB) Scan?
Nuchal translucency (NT), Nasal Bone (NB) scan is a screening test commonly done in the first trimester between week 11 to week 13 of pregnancy.
The test measures the amount of clear tissue present at the back of the neck of the fetus. This is the NT scan or Nuchal Translucency Scan.
Usually, not many clear tissues or fluid are present at the back of the fetal neck. But too much clear fluid can indicate chromosomal anomalies.
NB scan or Nasal Bone Scan is done along with an NT scan to check the baby’s nasal bone where the absence of nasal bone can be a red flag for Down syndrome.
The need for NT NB Scan
The Nuchal translucency (NT), Nasal Bone (NB) scan is a predictive test and not a diagnostic test. This means NT NB can predict the possibility of an abnormality but cannot confirm the same.
The clear tissues at the back of the fetal neck disappear after week 15 of pregnancy. Hence, NT NB scans are ideally done at the end of the first trimester.
The human cell consists of 23 pairs of chromosomes, including a pair of sex chromosomes- XX in females and XY in males.
The addition or deletion of chromosomes or a segment of chromosomes can cause chromosomal abnormalities.
This scan predicts one of the below chromosomal abnormalities in the baby.