Table 2:

Traditional Prenatal Screening and Diagnostic Options Available in Ontario

Option	Components	Timing, weeks	Comments
Traditional Prenatal Screening Before 14 Weeks (First Trimester)
eFTS	One blood test Screens for trisomy 21 and trisomy 18, but not open neural tube defects NT ultrasound	11–13	Results available in the first trimester after blood is taken (earliest results) CVS for confirmatory diagnostic testing Not available in all areas of Ontario
Traditional Prenatal Screening After 14 Weeks (Second Trimester)
MSS (or quadruple screening)	One blood test Screens for trisomy 21, trisomy 18, and open neural tube defects NT ultrasound is integrated into the test, if available	14–20	Results available in second trimester Amniocentesis for confirmatory diagnostic testing
Diagnostic Tests
CVS	—	11–13	—
Amniocentesis	—	Preferably 15–22	—

Abbreviations: CVS, chorionic villus sampling; eFTS, enhanced first-trimester screening; MSS, maternal serum screening; NT, nuchal translucency.

Source: Adapted from Prenatal Screening Ontario and Trillium Health Partners.^3–5