Trisomy 21 is positive in nuchal translucency. What does it indicate?

Q. In NT scan,Trisomy 21 screen is positive. What does it mean?

Answered by
Dr. Nadia Khan
and medically reviewed by Dr.Nithila A
This is a premium question & answer published on Aug 16, 2023

Hello doctor,

My wife is 36-year-old with a height of 5.6 and weight 152 lbs. She had NT or NB scan and double marker test in obstetrical ultrasound. The nuchal thickness is 1.0 mm. Presence of nasal bone. DV flow is normal, but in double marker test, free beta hCG is 46.20 and PAPP-A is 2.58. Trisomy 21 -screen positive cut off 1: 250. Mother's cut off free beta hCG is greater than or equal to 1.98 PAPP-A.



Welcome to

1 in 250 means that if we take 250 women of the same results as your wife had then only one will have a baby with Down syndrome. So this is the explanation of the calculated risk of Down syndrome. Secondly, NT (nuchal translucency) and blood tests which she underwent are screening tests. Screening tests are not diagnostic. They only detect who is at risk. If they become positive, that does not mean that particular is at risk. It just says that specific condition may or may not be there which is then confirmed by diagnostic tests. In your case, CVS (chorionic villus sampling, taking a sample from the baby) will diagnose if the Down syndrome is there or not which you will be offered at 12 to 13 weeks most probably. I hope it has helped you. If you require any further queries, please do not hesitate to contact me.

Was this answer helpful?


Same symptoms doesn’t mean you have the same problem. Consult a doctor now!

Related Questions:
What is the risk of trisomy 21 from my NT scan and double marker test?

.. gone through your question and understand the concerns. I have reviewed the report. It shows an increased risk in the first-trimester screening. You should go for amniocentesis at 16 weeks gestation to rule out any chromosomal anomalies in the fetus.   Read full

Is nasal bone length an indicator of Down's syndrome?

.. bone thickness is relevant only between 11 to 13 weeks pregnant scan where it should be less than 2 mm. Nasal bone thickness at 23 weeks gestation is irrelevant. If the quadruple test shows low risk of Down's syndrome, then amniocentesis is not recomm   Read full

Kindly explain the factors used to calculate the risk of trisomy 21.

.. gone through the query (attachment removed to protect patient identity). Many factors count for calculating risk. They are age, serum markers, family history, and nuchal translucency. An age-related risk is more after 35 years of age.   Read full

Also Read Answers From:

ideaComprehensive Medical Second Opinion.Submit your Case

Also Read

PCOS and Liver Problems
The hormonal imbalances in polycystic ovary syndrome could cause liver diseases. Read the article to know the relationship between these medical conditions.  Read more»
Inferior Alveolar Nerve Lateralization Technique
The inferior alveolar nerve lateralization technique is a surgical lateralization technique to reposition the nerve. Read the article to know more about this.  Read more»
COVID-19 and Ebola: Similarities and Differences
This article gives a comparison and broader overview of the outbreak of the two deadliest diseases that showed a greater incidence over the last two decades.  Read more»

Ask your health query to a doctor online?

Ask an Obstetrician & Gynaecologist Now

* guaranteed answer within 4 hours.

Disclaimer: No content published on this website is intended to be a substitute for professional medical diagnosis, advice or treatment by a trained physician. Seek advice from your physician or other qualified healthcare providers with questions you may have regarding your symptoms and medical condition for a complete medical diagnosis. Do not delay or disregard seeking professional medical advice because of something you have read on this website. Read our Editorial Process to know how we create content for health articles and queries.