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Table 4 Longitudinal reference percentiles of systolic: diastolic ratio (S/D) for IAA

From: Zone-specific reference ranges of fetal adrenal artery Doppler indices: a longitudinal study

GA (weeks) Percentile
2.5th 5th 10th 50th 90th 95th 97.5th
20 2.28 2.35 2.44 2.77 3.15 3.26 3.36
21 2.31 2.38 2.46 2.8 3.17 3.29 3.39
22 2.32 2.39 2.48 2.81 3.19 2.31 3.41
23 2.33 2.4 2.49 2.83 3.21 3.32 3.43
24 2.33 2.41 2.5 2.83 3.21 3.33 3.44
25 2.33 2.41 2.5 2.83 3.21 3.33 3.44
26 2.33 2.4 2.49 2.83 3.21 3.33 3.43
27 2.32 2.4 2.48 2.82 3.2 3.31 3.42
28 2.31 2.38 2.47 2.8 3.18 3.3 3.4
29 2.29 2.36 2.45 2.78 3.15 3.27 3.37
30 2.27 2.34 2.42 2.75 3.12 3.23 3.34
31 2.24 2.31 2.4 2.72 3.09 3.2 3.3
32 2.21 2.28 2.37 2.69 3.05 3.16 3.26
33 2.17 2.24 2.33 2.64 3 3.1 3.2
34 2.13 2.2 2.28 2.59 2.94 3.05 3.15
35 2.09 2.16 2.24 2.54 2.89 2.99 3.09
36 2.05 2.12 2.2 2.49 2.83 2.94 3.03
37 2 2.06 2.14 2.43 2.76 2.86 2.95
38 1.94 2 2.08 2.37 2.69 2.79 2.88
39 1.89 1.95 2.02 2.31 2.63 2.72 2.81
40 1.83 1.89 1.97 2.24 2.55 2.65 2.74
41 1.79 1.84 1.91 2.19 2.5 2.59 2.68