Ultrasonic Fetal Measurement Standards for an Australian Population - Compiled by Dr Susan Campbell Westerway

Oct 20, 2026

Ultrasonic fetal measurement standards for an Australian population compiled by Dr Susan Campbell Westerway present regression equations and grouped standard-deviation variability by gestational age. The approach adapts prior AC variability methods by averaging SD changes across gestational week groups rather than using a separate SD each week. Cross-sectional data are based on 11,600 measurements from 3,800 women across 70 nationalities, expressed for parameters including BPD, OFD, head circumference, abdominal circumference, femur, humerus, and related regression and SD models.

LanguageEnglish

CategoryHealthcare

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Pages8

Reading Time20 min

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Ultrasonic Fetal Measurement Standards for an Australian Population

Data collection and gestational age basis

Summary tables of +/- 2 standard deviations

Crown-rump length and gestation references

Regression analysis: CRL, BPD, OFD, HC, AC, FL, HL

Standard deviation regressions for fetal measurements

Susan Campbell Westerway PhD (Medicine) DMU MAppSc AMS Please note the changes to the standard deviations for both head and abdominal circumferences. I have adapted the technique of Deter et al (whose AC chart had been used by ASUM prior to mine) to simplify variability with gestational age. Thus, instead of having the SD at each week vary, the weeks have been grouped and the variations of standard deviations then averaged. Australasian Society for Ultrasound in Medicine Ultrasonic Fetal Measurement Standards for an Australian Population Compiled by Dr Susan Campbell Westerway – University of Sydney Gestation BPD OFD Head Abdominal Femur Humerus Gestation (weeks) (mm) (mm) circ. Circ.(mm) (mm) (mm) (weeks) +/-2 standard deviations shown in brackets. | 11 | 16 (2.0) | 21 (2.0) | 59 (15) | 52 (10) | 8 (2.0) | 8 (3.0) | 11 | | --- | --- | --- | --- | --- | --- | --- | --- | | 12 | 20 (4.0) | 24 (2.0) | 70 (15) | 63 (10) | 10 (2.5) | 9 (2.0) | 12 | | 13 | 24 (4.0) | 29 (3.0) | 84 (15) | 74 (10) | 11 (2.5) | 11 (3.0) | 13 | | 14 | 28 (4.0) | 34 (3.0) | 96 (15) | 84 (10) | 15 (3.0) | 14 (4.0) | 14 | | 15 | 31 (4.0) | 38 (3.0) | 108 (15) | 96 (10) | 17 (3.5) | 17 (5.5) | 15 | | 16 | 36 (5.0) | 46 (3.0) | 128 (15) | 106 (10) | 22 (4.0) | 21 (4.0) | 16 | | 17 | 39 (5.0) | 50 (3.0) | 141 (15) | 120 (15) | 25 (4.0) | 25 (5.0) | 17 | | 18 | 42 (4.0) | 54 (3.5) | 151 (20) | 131 (15) | 28 (5.0) | 27 (5.5) | 18 | | 19 | 45 (5.0) | 57 (3.5) | 160 (20) | 140 (15) | 30 (5.0) | 29 (5.0) | 19 | | 20 | 47 (4.0) | 61 (3.5) | 170 (20) | 151 (15) | 32 (6.0) | 31 (5.0) | 20 | | 21 | 49 (4.0) | 63 (4.0) | 176 (20) | 164 (20) | 34 (6.0) | 32 (6.0) | 21 | | 22 | 52 (5.0) | 68 (3.5) | 188 (20) | 176 (20) | 37 (5.0) | 35 (6.0) | 22 | | 23 | 57 (5.0) | 76 (4.0) | 210 (20) | 186 (20) | 43 (5.0) | 38 (4.0) | 23 | | 24 | 60 (6.0) | 79 (4.0) | 220 (20) | 201 (20) | 45 (4.0) | 40 (6.0) | 24 | | 25 | 64 (6.0) | 82 (4.5) | 231 (20) | 212 (20) | 48 (5.0) | 43 (5.0) | 25 | | 26 | 67 (4.0) | 84 (4.5) | 238 (20) | 223 (25) | 49 (5.0) | 44 (4.0) | 26 | | 27 | 68 (5.0) | 86 (4.5) | 250 (20) | 230 (25) | 50 (5.0) | 47 (4.0) | 27 | | 28 | 72 (4.0) | 95 (5.0) | 263 (20) | 242 (25) | 54 (4.0) | 50 (5.0) | 28 | | 29 | 75 (4.0) | 97 (5.5) | 269 (25) | 259 (25) | 55 (5.5) | 51 (5.0) | 29 | | 30 | 76 (4.0) | 98 (5.5) | 274 (25) | 262 (25) | 58 (6.0) | 52 (5.0) | 30 | | 31 | 80 (6.0) | 101 (5.0) | 284 (25) | 272 (30) | 59 (5.5) | 54 (5.0) | 31 | | 32 | 81 (4.0) | 102 (5.0) | 288 (25) | 283 (30) | 62 (6.0) | 56 (5.0) | 32 | | 33 | 84 (6.0) | 107 (5.5) | 300 (25) | 294 (30) | 65 (4.0) | 57 (6.0) | 33 | | 34 | 86 (6.0) | 108 (5.5) | 305 (25) | 305 (30) | 66 (4.0) | 59 (5.5) | 34 | | 35 | 88 (6.5) | 109 (5.5) | 310 (25) | 315 (30) | 67 (6.0) | 60 (6.0) | 35 | | 36 | 90 (6.0) | 112 (5.5) | 317 (25) | 325 (35) | 69 (6.0) | 62 (5.0) | 36 | | 37 | 92 (6.5) | 113 (6.0) | 321 (25) | 333 (35) | 72 (5.0) | 63 (6.0) | 37 | | 38 | 93 (6.0) | 116 (5.5) | 328 (25) | 342 (35) | 73 (5.5) | 64 (6.0) | 38 | | 39 | 95 (8.0) | 119 (6.0) | 336 (25) | 356 (35) | 75 (6.0) | 65 (5.5) | 39 | | 40 | 96 (8.0) | 120 (6.0) | 340 (25) | 362 (35) | 76 (4.0) | 66 (6.0) | 40 | | 41 | 98 (8.0) | 122 (6.0) | 344 (25) | 367 (35) | 77 (5.0) | 68( 6.0) | 41 | This cross sectional study collected 11,600 measurements from 3,800 women representing 70 nationalities. Figures are based on completed weeks of gestation. Crown-rump length measurements (mm) at points in gestation (weeks/days) | Gestation | CRL | Gestation | CRL | Gestation | CRL | | --- | --- | --- | --- | --- | --- | 5.2 5.3 5.4 5.5 5.6 6 6.1 6.2 6.3 6.4 6.5 6.6 7 7.1 7.2 7.3 7.4 7.5 7.6 8 8.1 8.2 1 2 3 3 4 4 5 6 7 8 9 10 11 11 12 12 13 14 15 17 18 19 8.3 8.4 8.5 8.6 9 9.1 9.2 9.3 9.4 9.5 9.6 10 10.1 10.2 10.3 10.4 10.5 10.6 11 11.1 11.2 11.3 20 21 22 22 23 24 26 27 28 29 31 34 36 37 38

FAQs

How are the standard deviations for head and abdominal circumferences handled in these standards?

The method groups gestational weeks and averages the variations of standard deviations, instead of varying SD at each individual week.

What data set underpins the fetal measurement standards?

The cross-sectional study uses 11,600 measurements collected from 3,800 women representing 70 nationalities, based on completed weeks of gestation.

Which fetal measurements are modeled using regression analysis in the document?

Regression equations are provided for crown-rump length (CRL) and for measurements including BPD, OFD, head circumference (HC), abdominal circumference (AC), femur length (FL), and humerus length (HL).

Oct 20, 2026

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