Prenatal Genetics Service

Prenatal screening services in our region are offered by Mount Sinai Hospital (MSH), Toronto. Blood samples and requisitions with nuchal translucency measurements are sent to Toronto for analysis. The MSH requisition is required to order testing.

MSH Toronto offers enhanced First Trimester Screening (eFTS). Integrated Prenatal Screening (IPS) is no longer available. Second trimester screening (STS, also known as Maternal Serum Screening [MSS] or the quad screen) continues to be available for patients presenting to care at later gestations (14-21 weeks). For more information on prenatal screening in Ontario, please see Prenatal Screening Ontario.

Pregnant patients with a positive screen can access non-invasive prenatal testing (NIPT) as a secondary screen ordered by their health care provider, typically their family doctor or obstetrician, or can be referred to the Prenatal Genetics Service if they wish to pursue diagnostic testing (CVS or amniocentesis).

For information on prenatal screening in Quebec, please visit Québec Prenatal Screening Program | Gouvernement du Québec (quebec.ca)

Some pregnant Ontario patients are eligible for OHIP-funded NIPT as a primary screen. These include any patients who are carrying twins, patients who are 40 years of age or older at delivery, pregnancies in which the fetal nuchal translucency measurement is 3.5mm or greater, or if a pregnant patient had a previous pregnancy with trisomy 21, trisomy 18, or trisomy 13. Any physician can order NIPT for patients meeting one of these criteria.

OHIP-funded NIPT may also be available as a secondary screen to some patients, most commonly when there are fetal ultrasound findings. These patients can be referred to the Prenatal Genetics Service to determine eligibility and to order testing.

Some patients who do not meet provincial criteria for funded testing can opt to pay privately for testing.

For requisitions, more information, and guidance on ordering NIPT, please visit Non-Invasive Prenatal Testing (NIPT) Guide - Prenatal Screening Ontario

Some Quebec patients may also be eligible for their provincial NIPT, called TGPNI. Information about the Quebec TGPNI can be found on their website.

Additional information about NIPT can also be found at GEC-KO.

Non-invasive prenatal testing (NIPT)

GECKO on the run: A 3-page, evidence-based summary for healthcare providers. Features a bottom line, current Canadian recommendations, red flags to consider offer of NIPT, what the results mean, benefits and limitations of the test (Updated Jan 2023)

GECKO deep dive: An 8-page comprehensive evidence-based resource for healthcare providers. Features a bottom line, current Canadian recommendations, red flags to consider offer of NIPT, what the results mean, benefits and limitations of the test, NIPT for microdeletions/duplications and sex chromosome differences, twins and multiples in addition to references and links to provincial programs. (Updated Jan 2023)

The Genetics Clinic no longer accepts referrals for advanced maternal age (AMA; ≥ 40 years at delivery) as the sole indication for prenatal genetic counselling. Providers are instead directed to arrange NIPT (see the NIPT section above).

For patients having NIPT as a primary screen, no other serum screen (eFTS/STS) is indicated for trisomy risk assessment. These are redundant and pose an unnecessary cost to the healthcare system. However, a nuchal translucency (NT) ultrasound at around 12 weeks’ gestation can still be ordered without enrolling the patient in eFTS as the NT measurement can provide important clinical information for pregnancy risk assessment.

Please continue to refer:

• Pregnant patients ≥ 40 years at delivery who are requesting invasive diagnostic testing (CVS/amniocentesis) without prior screening. Patients who have received a low risk NIPT result will not be eligible for referral to Genetics unless additional risk factors have been identified.
• Pregnant patients with abnormal or high risk NIPT results. The SOGC recommends that no irreversible obstetric decisions be made in pregnancies with abnormal NIPT results without confirmatory invasive testing, as false positives do occur.
• Pregnant patients with unusual NIPT results. Examples include uninterpretable, “no call”, atypical results, and repeat (2 or more) test failures.

Some pregnant patients may be eligible for prenatal diagnosis. Chorionic villus sampling (CVS) may be offered between 11-15 weeks of pregnancy while amniocentesis can be offered after about 15-16 weeks of pregnancy. These options will be discussed in detail with eligible patients; additional information can be found at Diagnostic Testing - Prenatal Screening Ontario (bornontario.ca).