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Table 3 The predictive properties of the 5th and 95th percentiles of each facial ultrasound marker

From: Utility of fetal facial markers on a second trimester genetic sonogram in screening for Down syndrome in a high-risk Thai population

GA
(weeks)
PT (mm) NBL (mm) PT/NBL Ratio NBL/PT Ratio
5th 95th 5th 95th 5th 95th 5th 95th
14 1.06 2.47 3.18 4.74 0.34 0.56 1.80 2.80
15 1.40 2.81 3.75 5.31 0.36 0.57 1.74 2.71
16 1.71 3.11 4.25 5.81 0.37 0.59 1.69 2.63
17 1.99 3.40 4.67 6.23 0.39 0.60 1.66 2.55
18 2.24 3.65 5.02 6.58 0.40 0.62 1.59 2.47
19 2.47 3.88 5.29 6.85 0.42 0.63 1.54 2.40
20 2.66 4.07 5.48 7.04 0.43 0.65 1.50 2.33
21 2.83 4.24 5.61 7.16 0.45 0.66 1.46 2.27
22 2.97 4.38 5.65 7.21 0.46 0.68 1.42 2.21
  1. GA Gestational age (weeks), PT Prenasal thickness, NBL Nasal bone length