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  • What is Prenatal Screening?
    • What Do We Screen For?
    • Multiple Marker Screening (MMS)
    • Non-Invasive Prenatal Testing
    • Nuchal Translucency Ultrasound
    • Other Kinds of Screening
    • Less than 14 Weeks' Pregnant
    • 14-21 Weeks' Pregnant
    • Greater than 21 Weeks' Pregnant
    • For Twins or More Than Two Babies
    • COVID-19 and Prenatal Screening
  • Results and Next Steps
    • Multiple Marker Screening (MMS) Results
    • Non-invasive Prenatal Testing (NIPT) Results
    • Invasive Diagnostic Testing
  • Requisitions and Provider Tools
    • Multiple Marker Screening (MMS) Requisitions
    • Non-invasive Prenatal Testing (NIPT) Requisitions
    • Provider Tools
    • Facilities that offer Nuchal Translucency ultrasound
  • For Sonographers
    • NT Quality Assurance
    • Resources and Point of Care Tools
    • Facilities that offer Nuchal Translucency ultrasound
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HomeWhat is Prenatal Screening?Nuchal Translucency UltrasoundIncreased Nuchal Translucency
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Increased Nuchal Translucency

If you had a nuchal translucency (NT) ultrasound in the first trimester of pregnancy, it is important to understand what it means if the measurement is “increased” or “abnormal”.

What is an increased NT?

In Ontario, the current cut-off for the NT measurement to be considered “increased” is 3.5mm. If the measurement is increased, your health care provider will discuss options for further testing and follow-up.

Increased NT

Illustration adapted from Genetic Counseling Aids, 7th Edition, Copyright 2020, permission for use granted by Greenwood Genetic Center

What an increased NT might mean

Measuring the NT in the first trimester of pregnancy is one way to screen pregnancies for some common chromosome and structural differences, including:

  • trisomy 21 (Down syndrome)
  • other chromosome differences – e.g., trisomy 18, trisomy 13, Turner syndrome, triploidy
  • other genetic conditions – e.g., Noonan syndrome
  • structural abnormalities – e.g., cardiac (heart) defects

It is important to know that an increased NT measurement can also be seen in healthy pregnancies. If invasive diagnostic testing rules out chromosome differences, the vast majority of babies with an increased NT measurement will have a healthy outcome.

Next steps

If you have an increased NT measurement, you should be offered a referral to a genetics or Maternal Fetal Medicine (MFM) clinic to discuss options for further testing. Any further testing is optional but may include:

  • invasive diagnostic testing – e.g., chorionic villus sampling (CVS) or amniocentesis
  • non-invasive prenatal testing (NIPT) - NIPT is funded by OHIP when the NT measurement is increased, and can be ordered by your pregnancy care provider or geneticist / Maternal Fetal Medicine (MFM) specialist
  • detailed anatomy ultrasound
  • fetal echocardiogram - specialized ultrasound of the fetal heart

Find genetics services in your area.

  • What is Prenatal Screening?
    • What Do We Screen For?
      Toggle Section What Do We Screen For? Menu
      • Chromosomes
      • Trisomy 21 (Down syndrome)
      • Trisomy 18
      • Trisomy 13
      • Sex chromosome differences
    • Multiple Marker Screening (MMS)
      Toggle Section Multiple Marker Screening (MMS) Menu
      • Enhanced First Trimester Screening (eFTS)
      • Maternal Serum Screen (MSS)
    • Non-Invasive Prenatal Testing
      Toggle Section Non-Invasive Prenatal Testing Menu
      • NIPT Funding Criteria
    • Nuchal Translucency Ultrasound
      Toggle Section Nuchal Translucency Ultrasound Menu
      • Increased Nuchal Translucency
    • Other Kinds of Screening
    • Less than 14 Weeks' Pregnant
      Toggle Section Less than 14 Weeks' Pregnant Menu
      • Enhanced First Trimester Screening (eFTS)
      • Nuchal Translucency Ultrasound
        Toggle Section Nuchal Translucency Ultrasound Menu
        • Increased Nuchal Translucency
      • Non-invasive Prenatal Testing
    • 14-21 Weeks' Pregnant
      Toggle Section 14-21 Weeks' Pregnant Menu
      • Multiple Marker Screening (MMS)
      • Non-invasive Prenatal Testing
      • Detailed Anatomy Ultrasound
    • Greater than 21 Weeks' Pregnant
      Toggle Section Greater than 21 Weeks' Pregnant Menu
      • Non-invasive Prenatal Testing
      • Detailed Anatomy Ultrasound
    • For Twins or More Than Two Babies
    • COVID-19 and Prenatal Screening

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Prenatal Screening Ontario 
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401 Smyth Road 
Ottawa, ON K1H 8L1

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