What prenatal screening tests are currently available 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 Quadruple Screening (MSS).
In keeping with the 2017 joint SOGC-CCMG guidelines stating “Second trimester serum alpha fetoprotein screening to rule out open neural tube defects is no longer necessary unless there is a barrier to good quality ultrasound examination”, screening for open neural tube defects using second trimester MS-AFP has been discontinued. The primary screening test for the detection of fetal structural abnormalities, including neural tube defects, is a second trimester anatomical ultrasound with detailed fetal cranial and spinal imaging and assessment.
This second trimester anatomical 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.
Points to consider when offering prenatal screening:
1. 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 ≥10 weeks’ gestation (some private labs do offer testing ≥9 weeks), and is only covered by OHIP if certain criteria are met. (More information on NIPT for health care providers can be found here)
2. Does your patient have access to an accredited ultrasound lab offering nuchal translucency (NT) ultrasound?
- eFTS incorporates both NT ultrasound and maternal blood work
- 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
Table 1. Available prenatal screening tests and how they compare.
Updated November 2018
*Additional serum-only screening options vary by region for those patients with no access to certified NT ultrasound. Please contact your local screening laboratory for more information.
What is available for 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.