A nuchal translucency scan is a most awaited scan in your pregnancy journey. Because it is when you can see your bundle of joy for the first time on the monitor.
This could make you equally anxious, as this can help to roll out the possibility of your baby being born with major chromosomal disorders and birth defects. So, what does an abnormal NT scan denote? Let’s get into its details.
What Does An Abnormal NT Scan Mean?
An abnormal NT scan is when,
- The nuchal translucency fluid present at the back of the baby’s neck is thicker than expected for the gestation.
- The baby shows an absence of nasal bone.
- Or if the baby is identified with certain birth defects.
What Causes An Increase In NT?
An abnormal NT scan value is seen in babies with chromosomal abnormalities and structural anomalies, including cardiac defects, diaphragmatic hernias, body stalk anomalies, and skeletal defects. An increased NT has also been associated with a high risk of miscarriage.
What Happens If The NT Value Is High?
If your nuchal translucency scan shows an increased NT value, your chances of carrying a baby with chromosomal or birth defects increase.
How often are NT scans wrong?
NT scans have a 5% of false percentage.
And NT scans results, when obtained alone, have an accuracy rate of 70%, which can be increased when coupled with a Double marker test. This is a maternal blood test that studies certain hormone levels that can highly accurate the possibility of chromosomal disorders by 85%.
What Happens If The NT Scan Is Not Normal? – Diagnostic Tests Recommended after an abnormal NT scan
A nuchal translucency scan is part of your screening tests and cannot confirm your baby of any chromosomal or genetic disorders. So, it is advised that high-risk NT results should be followed by confirmatory diagnostic tests listed below.
Chorionic Villus Sampling:
CVS is an invasive procedure that diagnoses chromosomal abnormalities by collecting the placental tissues.
Amniocentesis is an invasive procedure where the amniotic fluid from the womb is collected to diagnose genetic disorders.
Noninvasive prenatal testing (NITP) is a non-invasive procedure that diagnoses chromosomal disorders in the baby in the womb.
These confirmatory tests also help find the type of chromosomal disorder your baby is affected with.
- Down syndrome or Trisomy 21
- Edward syndrome or Trisomy 18
- Patau syndrome or Trisomy 13
Studying the chromosome number that has the extra copy helps distinguish these syndromes. Down syndrome or Trisomy 21 is the most prevalent type seen in most babies of the types mentioned above.
Can A Baby With Down Syndrome Have Normal Nuchal Translucency?
A normal NT value indicates that it’s very unlikely that your unborn would be born with Down syndrome.
Normal babies generally show the right amount of nuchal translucency fluid level for gestational age.
Your doctor also looks for other soft markers, like a nasal bone, to confirm your baby’s condition.
Can you check for chromosomal disorders in the second trimester?
It is always recommended that you do not miss any pregnancy routine scans (NT scan during pregnancy internal link). But, if at any worst case, if you happen to miss your first trimester NT scan, a maternal blood test called the Quadruple test can be taken during your second trimester.
You can talk to your doctor about this.