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Ontario Prenatal Screening
Prenatal Screening Tests for the Detection of Down Syndrome
Prenatal Diagnostic Testing
Prenatal Screening Tests for the Detection of Down Syndrome

Prenatal Screening Tests for the Detection of Down Syndrome

 

Testing for Open Neural Tube Defects and Trisomy 18

Testing for Open Neural Tube Defects and Trisomy 18

Detection Rate (DR):
Also known as sensitivity, is the probability that a fetus affected with Down syndrome will be detected by the prenatal screening test.

False Positive Rate (FPR):
The proportion of women with unaffected pregnancies who have positive results.

Pregnancy Dating
Ultrasound (U/S) dating is more accurate than LMP; a dating U/S will lower the FPR.

All pregnancies have a 2-3% risk for any birth defect which may or may not be detected by prenatal screening.

Adapted from:
1. Wald NJ, et al. First and second trimester antenatal screening for Down’s syndrome: the results of the Serum, Urine and Ultrasound Screening Study (SURUSS). J Med Screen 2003; 10:56-104.

2. Malone FD, et al. First- and Second-Trimester Evaluation of Risk (FASTER)
Research Consortium. First-trimester or second-trimester screening, or both, for Down’s syndrome. N Engl J Med. 2005; 353:2001-11.
 
3. Wapner R, et al. First trimester screening for trisomies 21 and 18. N Engl J Med 2003; 349:1405 -1413.

4. Summers AS, et al. Maternal serum screening in Ontario using the triple marker test. J Med Screen 2003; 10:107-11.

5. American College of Obstetricians and Gynecologists. Clinical Management
Guidelines for obstetricians-gynecologists. ACOG Practice Bulletin No. 44, Obstet Gynecol 2003; 102:203-211.

For more information

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