Prenatal testing

Prenatal Screening (FTS/MSS)

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 First Trimester Screening (FTS). Earlier screening results allow a woman with a positive screen to access genetic counselling and/or non-invasive prenatal testing (NIPT) as a secondary screen or diagnostic testing sooner in her pregnancy. Integrated Prenatal Screening (IPS) is no longer available. Maternal Serum Screening (2nd trimester) continues to be available for patients presenting to care at later gestations.

If your patient receives a positive prenatal screening result and would like an appointment in the Prenatal Genetics Clinic at CHEO, you must refer her to the Genetics Clinic.

For more information on prenatal screening in Ontario, please see Prenatal Screening Ontario.

For more information on prenatal screening in Quebec, please see the Quebec prenatal screening program.

Non-invasive prenatal testing (NIPT)

Prenatal testing guide for women

Advanced maternal age (AMA)

Prenatal genetic counselling for advanced maternal age (AMA) has been discontinued

• Please be aware that as of June 1, 2017, the Genetics Clinic no longer accepts referrals for advanced maternal age (AMA) as the sole indication for prenatal genetic counselling.
• Any physician can arrange an OHIP or RAMQ-funded non-invasive prenatal test (NIPT) for the indication of AMA without a referral to Genetics (see information and link below).
• For women having NIPT as a primary screen, no other serum screen (FTS/MSS) is indicated for trisomy risk assessment. These are redundant and pose unnecessary cost to the system.
• A Guide to Understanding Prenatal Screening Tests, a new, comprehensive guide for patients and their providers on prenatal screening, is available to assist you (see information and link below).

Why the change?

• NIPT has dramatically changed the landscape of prenatal screening.
• NIPT uses cell-free fetal DNA in maternal blood to screen for fetal trisomies.
• NIPT has much higher sensitivity and specificity than traditional screening methods (FTS/MSS).
• NIPT has been available as an OHIP-funded test for AMA women (≥ 40 yrs at delivery) since March 2014.
• NIPT has significantly decreased the number of amniocentesis procedures performed in our region.
• Like most medical clinics, we have very long wait lists and competing demands. Now that prenatal screening is simpler for AMA patients and their providers, we must redirect resources to other services within our clinic.
• Any physician can arrange NIPT for the indication of advanced maternal age without a referral to Genetics.
• Test information and links to requisitions for Ontario patients can be found on the GEC-KO website.
• Test information and links to requisitions for Quebec patients can be found on the Quebec prenatal screening program website.

Please continue to refer:

• AMA women requesting invasive testing (CVS/amniocentesis) without prior screening. Women who have received a low risk NIPT result will not be eligible for referral to Genetics unless additional risk factors have been identified.
• Women age 35 or older at delivery who are carrying twins. OHIP-funded NIPT can be arranged for this population, but only by an MFM specialist or Geneticist. RAMQ-funded NIPT is not validated for twin pregnancies and is not available for women carrying twins at this time.
• Women with abnormal 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.
• Women with unusual NIPT results. Examples include uninterpretable results, “no call” results, intermediate risk results and repeat test failures.

Helpful tips:

• All women less than age 40 at delivery should continue to be offered traditional prenatal screening (FTS/MSS). However some women may choose to self-pay for NIPT.
• For women 40 or older at delivery, in addition to NIPT you may still order a nuchal translucency measurement at around 12 weeks gestation without enrolling your patient in FTS.

New patient resource

A Guide to Understanding Prenatal Screening Tests is a new, comprehensive and updated guide on prenatal screening published in March 2017 for patients and their providers that can be referred to throughout the screening process. This guide was written by a multidisciplinary team and informed by input from new parents. Copies can be viewed online or printed from: Genetics Education > Public Resources > Prenatal and Preconception Genetics.

The Quebec prenatal screening program published the Guide informationnel destiné aux professionnels de la santé (french only) and a pamphlet for patients in 2020. The pamphlet present all the information on the Québec Prenatal Screening Program to help pregnant women and couples to make a informed decision to whether or not they want to participate.