Q. What is the risk of trisomy 21 from my NT scan and double marker test?

Answered by
Dr. Deepti Verma
and medically reviewed by iCliniq medical review team.
This is a premium question & answer published on Apr 16, 2018 and last reviewed on: Nov 16, 2022

Hi doctor,

I had an NT scan and a double marker test at 12 weeks and five days of pregnancy. The report is as follows.

  • Maternal serum screen 2: Dual test. (CLIA)

HCG, Free Beta 69.00 ng/mL equivalent to 1.81 Corr.MOM's

PAPP-A 1.40 mIU/mL equivalent to 0.36 Corr.MOM's

  • Disorder screen positive cut off

Trisomy 21 (Down) 1:250

Trisomy 18/13 1:100

  • Ultrasound data

CRL 62.9mm

Gestational age by CRL 12 + 4

Gestation age on the day of serum taking 12 + 5

Nuchal Translucency 2.00mm

NT'Mom's 1.23Mom

Nasal Bone Present

Measured by a radiologist.

  • Trisomy 21 Screening

Screen positive

'The calculated risk for Trisomy 21 (with nuchal translucency) is above the cutoff, which indicates an increased risk. After the result of the Trisomy 21 test (with NT) it is expected that among 156 women with the same data, there is one woman with trisomy 21 pregnancy and 155 women with not affected pregnancies.The PAPP-A level is low.The calculated risk by PRISCA depends on the accuracy of the information provided by the referring physician.'

I wanted to know about the risk if in the first-trimester screening window is positive.

Please suggest.



Welcome to

I have gone through your question and understand the concerns. I have reviewed the report (attachment removed to protect the patient's identity). 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.

Hope you found the answer helpful.


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