Prenatal Genetic Screening

What is it?

• Prenatal genetic screening tests focus on the chance of your baby having a chromosomal abnormality such as trisomy 18 or trisomy 21 (Down syndrome), two genetic conditions that cause intellectual disability and health challenges.
• Prenatal genetic screening is available to all pregnant people in Ontario; it’s your choice whether you have it or not.
• Being screened presents no risk to the pregnancy because it’s done by ultrasound and blood work.
• Any person can have a baby with trisomy 18 or trisomy 21 (even if no one else in their family has). The chance of it happening increases as the pregnant person gets older.
• Prenatal genetic screening can only let you know if the baby's chance of having certain genetic conditions is higher or lower, and you can then consider further tests that will say for sure. Prenatal genetic screening does not tell you if your baby definitely has a genetic condition.

What are my options?

1. Enhanced First Trimester Screening (eFTS)
   • This screen is paid for by the Ontario Health Insurance Plan (OHIP) from 11 weeks and 2 days to 13 weeks and 3days of pregnancy. It involves a special ultrasound called the 11-14 week(nuchal translucency) ultrasound and a blood test and finds most pregnancies with trisomy 18 and 21, but not all.
2. Non-Invasive Prenatal Testing(NIPT)
   • NIPT is a blood test that can be done any time after 9 or 10 weeks of pregnancy, depending on the laboratory.
   • It can find more pregnancies with trisomy 18 and 21 than the above screen. NIPT also screens for another genetic condition called trisomy 13.
   • NIPT is OHIP-funded if you meet one of the funding criteria, which include:
     • You will be age 40 or older at the time of birth.
     •  You had a past pregnancy with trisomy 18, 21, or 13.
     • You are pregnant with twins.
   •  If you do not meet the criteria but still want NIPT, you can pay for it yourself (~$500). Your primary health-care practitioner will still need to organize it for you.
   •  If you choose NIPT, you don't need enhanced first or second trimester screening, but it’s still recommended you have a 11-14 week ultrasound (without the blood test) for more information about the health of the baby.
3. Nuchal translucency ultrasound
   • This is an ultrasound done between 11-14 weeks. The ultrasound measures the clear fluid at the back of the baby’s neck. When there is more fluid seen than normal, there is a higher chance of genetic conditions or another health issue.
   • It can be done as part of enhanced first trimester screening or on its own.
   • It is recommended to have done regardless if genetic testing was completed or not.

Is prenatal genetic testing right for me?

Deciding whether to have prenatal genetic screening is up to you and there is no right or wrong choice. Thinking about these questions might help you make a decision.

Do you want to know if there is an increased chance of your baby having a genetic condition that could affect their health and development?

Many parents, but not all, want to know the chance of the baby having trisomy 18 or 21. Some want to know if there's a higher chance of the baby having a genetic condition so that they can decide what to do next, while others hope for the reassurance of being told there's a low chance. Some are worried they’ll get a false positive, where the screening says the baby has an increased chance of a genetic condition but in fact they don’t. That happens more often with two of the screens described here (enhanced First Trimester Screening and Second Trimester Screening).

Would you have further diagnostic testing if your screening results show there is a higher chance for trisomy 18or 21?

There’s a small risk the tests that diagnose trisomy 18 and 21 (chorionic villus sampling and amniocentesis) will cause miscarriage, but they’re the only way to be sure if the baby has either condition.

What are your thoughts about continuing or ending a pregnancy with trisomy 18 or 21?

Your decision needs to be right for you, depending on your life situation, values and beliefs. Speaking with health-care practitioners, family, friends or counsellors and learning about further tests might help you make your choice.

Would knowing about one of these genetic conditions help you prepare for it?

Some people who continue their pregnancy find it helpful to have the extra time to learn more about trisomy 18 or 21,and what local resources are available or perhaps to make an adoption plan for the baby.

What could the result mean for your pregnancy care?

Prenatal genetic screening can lead to more prenatal care and monitoring. Even if you don’t have a follow-up diagnostic test but there are signs of a genetic condition or other concerns, your care may change.

Who will order my testing?

Please see your primary care provider to order genetic testing or to further discuss options.

For more information visit prenatalscreeningontario.ca

Reference:

Prenatal Screening Ontario. Prenatal Screening Ontario. Government of Ontario. Retrieved from https://www.prenatalscreeningontario.ca

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