Table 27:

Expected Target Population for Prenatal Screening in Ontario

Population	Year 1	Year 2	Year 3	Year 4	Year 5
Total newborns	150,204	151,706	153,223	154,755	156,303
Newborns from a multiple-gestation pregnancy	4,730	4,730	4,730	4,730	4,730
Total singleton births	145,474	146,976	148,493	150,025	151,573
Births to average-risk pregnant peoplea	138,200	139,627	141,068	142,524	143,994
Average-risk pregnant people at 12 weeks’ gestationb	142,346	143,816	145,300	146,800	148,314
Average-risk pregnant people who choose prenatal screeningc	96,602	97,600	98,607	99,625	100,653
First trimester (90%)	87,116	88,016	88,924	89,842	90,769
Second trimester (10%)	9,486	9,584	9,683	9,783	9,884

Note: Some numbers may appear inexact due to rounding.

^aAccording to data for 2014–2016 from the Better Outcomes Registry and Network (BORN), 4.2% of people were ≥ 40 years old at time they delivered.⁸² Assuming that a very small proportion of pregnant people had a previous pregnancy with a chromosomal anomaly, approximately 95% of people would fall into in the average-risk category.

^bAssuming a spontaneous pregnancy loss background risk of 3% between 12 weeks (first trimester) and term, ^94,99 we estimated that the number of average-risk people with a singleton pregnancy during the first trimester would be approximately equal to the estimated number of average-risk people multiplied by 1.03 (e.g., 138,200 × 1.03 = 142,346 in year 1).

^cThe uptake rate for prenatal screening is approximately 68% among average-risk pregnant people in Ontario (BORN data).