[Glossary] OB calculations

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  • GA: Gestational Age.
  • Fetal age: Conceptional age.
  • EFW: Estimated fetal weight.
  • AUA: Arithmetic ultrasound age.
  • DOC: Date of conception.
  • LMP: Last menstrual period.
  • EDD: Estimated due date.

In Early OB

  • CRL: Crown-rump length
  • GS: Gestational sac.

In Mid-late OB

  • AC: Abdominal circumference.
  • HC: Head circumference.
  • FL: Femur length.
  • BPD: Biparietal diameter.

References

  1. Early OB calculations: Hadlock 1992.
    Fetal Crown-Rump Length: Reevaluation of Relation to Menstrual Age with High-Resolution Real-Time US.
  2. Mid-late OB calculations: Hadlock 1984
    Hadlock F.P, Deter R.L, Harrist R.B. and Park S.K, Estimating fetal age: computer-assisted analysis of multiple fetal growth parameters, Radiology, 152, pp 497-501, 1984
  3. EFW equations:
    EFW by AC, BPD FL, and HC: Hadlock 1985
    Hadlock F.P, Harrist R.B, Sharman R.S, Deter R.L, Park S.K, Estimation of fetal weight with the use of head, body, and femur measurements–a prospective study, Am.J.Obstet.Gynecol., 151, pp 333-337, 1985

Appendix Tables

CRL (cm)GA (weeks)
0.2220175
0.3232575.5
0.4582216
0.6330766.5
0.8534557
1.123937.5
1.447498
1.825178.5
2.255759
2.735699.5
3.2592610
3.8188910.5
4.4056411
5.0098611.5
5.6217812
6.2322312.5
6.8331913
7.4182813.5
7.9830814
8.525414.5
9.0453415
9.5453115.5
10.0316
10.506116.5
10.982617
11.470417.5
11.982618
12.534618.5
13.144619
13.834219.5
GS (mm)Fetal age (weeks)
22.985714286
33.114285714
43.228571429
53.357142857
63.485714286
73.614285714
83.742857143
93.871428571
103.985714286
114.114285714
124.242857143
134.371428571
144.5
154.614285714
164.742857143
174.871428571
185
195.128571429
205.257142857
215.371428571
225.5
235.628571429
245.757142857
255.885714286
266
276.128571429
286.257142857
296.385714286
306.514285714
GA (weeks)AC (cm)HCFL
124.582886.799710.7244
12.55.265627.522340.89625
135.943388.24021.0664
13.56.616158.95311.23485
147.283929.660831.4016
14.57.946710.36321.56665
158.604511.06011.73
15.59.2573111.75121.89165
169.9051212.43632.0516
16.510.547913.11542.20985
1711.185813.78822.3664
17.511.818614.45442.52125
1812.446515.1142.6744
18.513.069315.76672.82585
1913.687216.41232.9756
19.514.300117.05073.12365
2014.90817.68163.27
20.515.510918.30493.41465
2116.108818.92033.5576
21.516.701719.52773.69885
2217.289720.12693.8384
22.517.872620.71773.97625
2318.450621.29984.1124
23.519.023521.87324.24685
2419.591522.43764.3796
24.520.154522.99294.51065
2520.712523.53884.64
25.521.265524.07514.76765
2621.813524.60164.8936
26.522.356525.11835.01785
2722.894625.62485.1404
27.523.427626.1215.26125
2823.955726.60665.3804
28.524.478727.08165.49785
2924.996827.54575.6136
29.525.509927.99875.72765
3026.01828.44045.84
30.526.521128.87075.95065
3127.019229.28936.0596
31.527.512329.6966.16685
3228.000530.09076.2724
32.528.483630.47326.37625
3328.961830.84336.4784
33.529.434931.20076.57885
3429.903131.54536.6776
34.530.366331.8776.77465
3530.824532.19556.87
35.531.277732.50056.96365
3631.725932.79217.0556
36.532.169133.06987.14585
3732.607433.33367.2344
37.533.040633.58337.32125
3833.468933.81867.4064
38.533.892134.03947.48985
3934.310434.24557.5716
39.534.723734.43677.65165
4035.13234.61287.73
GA (weeks)BPD (cm)
12.54381.7
12.96081.9
13.39132.1
13.83522.3
14.29252.5
14.76322.7
15.24732.9
15.74483.1
15.99863.2
16.51633.4
17.04733.6
17.59173.8
17.8693.9
18.43364.1
19.01154.3
19.60294.5
19.90364.6
20.51514.8
21.145
21.45755.1
22.10255.3
22.76095.5
23.09515.6
23.77375.8
24.1185.9
24.81666.1
25.17096.2
25.88976.4
26.25416.5
26.9936.7
27.36746.8
27.74526.9
28.51097.1
28.89887.2
29.297.3
30.08257.5
30.48387.6
30.88847.7
31.29647.8
31.70777.9
32.54048.1
32.96188.2
33.38668.3
33.81478.4
34.24618.5
34.68098.6
35.1198.7
35.56058.8
36.00548.9
36.45369
36.90529.1
37.36019.2
37.81839.3
38.27999.4
38.74499.5
39.21329.6
39.68499.7
40.15999.8
40.63839.9
41.1210
41.605110.1
42.093510.2
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