Group | Week of gestation | Risk for trisomy 21 (Cut-off ≤1:300) N/Total (%) | Risk for trisomy 18 (Cut-off ≤1:100) N/Total (%) | Between-weeks' difference * |
---|---|---|---|---|
1 | 10 to 10+6/7 | 15/96 (16.1%) | 2/96 (2.2%) | / |
2 | 11 to 11+6/7 | 109/853 (12.8%) | 17/853 (2.0%) | Group 1 vs. Group 2 χ2=0.402, p = 0.52 |
3 | 12 to 12+6/7 | 158/1326 (11.9%) | 15/1326 (1.1%) | Group 2 vs. Group 3 χ2=0.313, p = 0.58 |
4 | 13 to 13+6/7 | 60/608 (9.9%) | 10/608 (1.6%) | Group 3 vs. Group 4 χ2=0.813, p = 0.37 |