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  • What We Screen For In Ontario
    • Trisomy 21 (Down Syndrome)
    • Trisomy 18 (Edwards Syndrome)
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  • Prenatal Screening Options
    • Is Prenatal Screening Right For Me?
    • Less than 14 Weeks' Pregnant
    • 14-21 Weeks' Pregnant
    • More than 21 Weeks' Pregnant
    • Twins and More Than Two Babies
    • Vanishing Twins
  • Results and Next Steps
    • Enhanced First Trimester Screening Results
    • Second Trimester Screening Results
    • Screening for Vanishing Twins Results
    • Non-invasive Prenatal Testing (NIPT) Results
    • 11-14 Week (Nuchal Translucency) Ultrasound Results
    • 18-22 Week Ultrasound Results
    • Diagnostic Testing
  • For Providers-How to Order
    • enhanced First Trimester Screening (eFTS) Guide
    • Second Trimester Screening (STS) Guide
    • Non-Invasive Prenatal Testing (NIPT) Guide
    • Screening for Vanishing Twins Guide
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HomePrenatal Screening OptionsVanishing Twins
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Vanishing Twins

If your pregnancy started as a twin pregnancy and one twin miscarried, this is sometimes called a "vanishing" twin pregnancy. 

Choose which statement is true for you to see your options for prenatal genetic screening:

I am in the first trimester of pregnancy and I can have a 11-14 week (nuchal translucency) ultrasound.

You can have an ultrasound and a blood test organized by your health-care provider. The following steps can be followed: 

  1. Get a 11-14 week (nuchal translucency) ultrasound in the first trimester of pregnancy (when you are about 3 months pregnant). There should be no prenatal screening blood work done on the day of this ultrasound. The "Multiple Marker Screening" requisition form will be filled out at the time of the ultrasound. It is important that you keep this requisition in a safe place because it will be needed for blood work later in the pregnancy. 
  2. Go for Second Trimester Screening (STS) blood work in the second trimester (when you are about 4 or 5 months pregnant). You must wait until at least 8 weeks have passed from the miscarriage of the twin.

Download Step-by-Step Instructions 

How does the screening work?

This screening test will combine all the information below to tell you about the chance to have a baby with trisomy 21 and trisomy 18:

Your age at the time of birth

You have a higher chance for chromosome differences like trisomy 21 and trisomy 18 as you get older. If you got pregnant through in vitro fertilization, it is the age of the egg that is used. The egg may be your own or from a donor. 

11-14 week (nuchal translucecy) ultrasound result

The nuchal translucency (NT) refers to the pocket of fluid at the back of the baby's neck. This pocket of fluid is measured during the ultrasound. When there is more fluid than what we typically see, there is an increased chance for trisomy 21, trisomy 18 and other conditions. 

Blood draw result

The blood test for STS will measure the amount of  4  chemicals made by your pregnancy. 

Other information about you

Your health-care provider will ask you some questions about you that improve the accuracy of test. You will be asked about your racial identity, diabetes status, smoking history in the pregnancy, weight and whether the pregnancy happened through in vitro fertilization. 

How long does it take to get results?

The results will be shared with your health-care provider within about 5 working days after your blood work. Keep in mind that your provider may not get the report right away. Talk to your provider about how they plan to give you these results.

What type of results will I get?

When you get your report, it will most likely say that you have a  “screen negative” result. This means that you have a lower chance to have a baby with trisomy 21 and trisomy 18.  It does not mean "no chance". 

Some individuals will get a  “screen positive” result, which means that there is a higher chance to have a baby with trisomy 21 or trisomy 18. It does not mean your baby definitely has one of these chromosome differences.  You would have more options for testing, including diagnostic testing. 

I am in the first trimester of pregnancy but I am not able to have a 11-14 week (nuchal translucency) ultrasound.
You can have Second Trimester Screening (STS) blood work on its own in the second trimester of pregnancy (between 14 weeks and 20 weeks 6 days). You must wait until at least 8 weeks have passed from the miscarriage of the twin. This testing can be organized by your health-care provider. 
I am in the second trimester of pregnancy and have not had a 11-14 week (nuchal translucency) ultrasound.
You can have Second Trimester Screening (STS) blood work on its own (between 14 weeks and 20 weeks 6 days of pregnancy). You must wait until at least 8 weeks have passed from the miscarriage of the twin. This testing can be organized by your health-care provider. 

It is important to know that Non-Invasive Prenatal Testing (NIPT) and enhanced First Trimester Screening (eFTS) cannot be done if you had a "vanishing" twin. This is because there can still be genetic material (DNA) or hormones in your blood from the twin that miscarried, and this can make the testing less accurate. 

female provider
For Health-Care Providers
Screening for Vanishing Twins Guide
  • Prenatal Screening Options
    • Is Prenatal Screening Right For Me?
    • Less than 14 Weeks' Pregnant
      Toggle Section Less than 14 Weeks' Pregnant Menu
      • Enhanced First Trimester Screening (eFTS)
      • Non-Invasive Prenatal Testing (NIPT)
        Toggle Section Non-Invasive Prenatal Testing (NIPT) Menu
        • NIPT Funding Criteria
      • 11-14 Week (Nuchal Translucency) Ultrasound
    • 14-21 Weeks' Pregnant
      Toggle Section 14-21 Weeks' Pregnant Menu
      • Second Trimester Screening (STS)
      • Non-Invasive Prenatal Testing (NIPT)
        Toggle Section Non-Invasive Prenatal Testing (NIPT) Menu
        • NIPT Funding Criteria
      • 18-22 Week Ultrasound
    • More than 21 Weeks' Pregnant
      Toggle Section More than 21 Weeks' Pregnant Menu
      • Non-Invasive Prenatal Testing (NIPT)
        Toggle Section Non-Invasive Prenatal Testing (NIPT) Menu
        • NIPT Funding Criteria
      • 18-22 Week Ultrasound
    • Twins and More Than Two Babies
    • Vanishing Twins

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