Table 1 Characteristics of the study population
Parameter | Euploid fetuses (n = 340) | Fetuses with Down syndrome (n = 11) | P value |
|---|---|---|---|
Maternal age (median, years) | 35 (32,37.25) | 39 (34.5,39.5) | 0.0788 |
Gestational age at ultrasound (median, weeks) | 17 (16,20) | 18 (18,20) | 0.0887 |
PT (mm) median (min,max) | 2.73 (2.33,3.3) | 4.8 (4.1,5.2) |  < 0.001 |
NBL (mm) median (min,max) | 5.4 (5,6.1) | 1.4 (1.07,1.8) |  < 0.001 |
PT/NBL ratio median (min,max) | 0.5 (0.46,0.55) | 3 (2.65,4.7) |  < 0.001 |
NBL/PT ratio median (min,max) | 2 (1.81,2.18) | 0.33 (0.2,0.38) |  < 0.001 |