You have reviewed the benefits and limitations of prenatal testing with your patient/client and they have elected to proceed with screening.
Be sure to consider the following factors when discussing which screening test is best:
- How far along is your patient?
- enhanced First Trimester Screening (eFTS) is available between 11-13+6 weeks
- Maternal Serum Screen (MSS)-Quad is available for patients 15-20+6 weeks
- Non-invasive Prenatal Testing (NIPT) is available to those ≥9 weeks, with current SOGC guidelines recommending that NIPT/cfDNA be performed after 10 weeks’ gestation, and is only covered by OHIP if certain criteria are met (click here for the current criteria for MOH-funded NIPT)
- Does your patient have access to an accredited ultrasound lab offering nuchal translucency (NT) ultrasound?
- eFTS incorporates both NT ultrasound and bloodwork
- serum-only screening is available for those without access to NT-accredited ultrasound clinics, for further information on regional options, please contact your local screening lab
What are the current prenatal screening options in Ontario?
Because prenatal screening is moving toward results available earlier in pregnancy, allowing expectant couples more time for decision making and access to additional services, integrated prenatal screening (IPS) is no longer available in Ontario. Most centres are now offering enhanced FTS (eFTS). This improved test performs better than traditional FTS with a higher detection rate and lower false positive rate. eFTS is expected to be just as good as IPS, but with results available earlier in pregnancy.
Enhanced first trimester screening (eFTS) is the most commonly offered prenatal screening test. It offers screening for Down syndrome and trisomy 18, with results available 7-10 days from the time of the blood draw.
When access to a certified ultrasound site to measure the nuchal translucency is not possible, serum-only prenatal screening may be offered. The type and timing of serum-only screening differs regionally. Please contact your local serum lab for details.
A pregnant person who presents to their first prenatal visit at a later gestational age (after 14 weeks) may be offered Maternal Serum Quad Screening (MSS).
An ultrasound is recommended for all pregnant persons at about 18-20 weeks of pregnancy to look at the baby’s growth and anatomy, regardless of prenatal screening results. While most babies are born healthy, 1 in 25 babies in Canada will be born with a difference that may require medical intervention. It is important to remember that no test can detect every type of congenital anomaly.
Screening options in twin pregnancies
If your patient is expecting twins, prenatal screening is available but in general is not as good as for pregnancies with one baby. At this time, both eFTS and MSS-Quad are available in twin pregnancies.
Table 1. Prenatal screening tests available and how they compare.
Updated June 2018
|Enhanced First Trimester Screening (eFTS)||Non-Invasive Prenatal Testing (NIPT)/cfDNA screening||Serum Integrated Prenatal Screening (SIPS)||Maternal Serum Screening (MSS)|
|Components of test|
All screens use pregnant person’s age in chance assessments
u/s = ultrasound
NT = nuchal translucency
|Gestational age at first trimester blood test||11 – 13 weeks + 6 days||9-10 weeks onward||11 – 13 weeks+6 days||Not applicable|
|Gestational age at the NT ultrasound||11 – 13 weeks + 6 days||Not applicable||Not applicable||Not applicable|
|Gestational age at second trimester blood test||Not applicable||Not applicable||15 – 20 week + 6 days||15 – 20 week + 6 days|
|Detection rate||Meaning, how many pregnancies where the baby really does have Down syndrome will be flagged as increased chance (screen positive) by this test?|
|False positive rate||Meaning, how many pregnancies will this test flag as increased chance (screen positive) BUT the baby does NOT really have Down syndrome?|
|about 3-6%||Less than 0.1%||about 2-7%||about 5%|
|Conditions screened for|