Measurements Frequently Used to Estimate Gestational Age and Fetal Biometry







TABLE A-1

Methods for Determining Menstrual Age

Adapted from Frank P. Hadlock, MD, and James D. Bowie, MD.








































Clinical or Sonographic Parameter Variability Estimate (2 SD)
In vitro fertilization * ±1 day
Ovulation induction * ±3 days
Artificial insemination * ±3 days
Single intercourse record * ±3 days
Basal body temperature record * ±4 days
First trimester physical examination ±2 weeks
Second trimester physical examination ±4 weeks
Third trimester physical examination ±6 weeks
First trimester sonographic examination (CRL) ±8% of the estimate
Second trimester sonographic examination (HC, FL) ±8% of the estimate
Third trimester sonographic examination (HC, FL) ±8% of the estimate

CRL, crown-rump length; FL, femur length; HC, head circumference.

* Indicators of conceptual age (menstrual age = conceptual age + 14 days).



TABLE A-2

Normal Transvaginal Sonographic Findings in the Early First Trimester












































Gestational Age (wk) Structure First Appears on Ultrasound * Mean Sac Diameter (mm) 8 Crown-Rump Length (mm) 10
5.0 Gestational sac 2
5.5 Yolk sac 6
6.0 Embryo with heartbeat 10 3
6.5 14 6
7.0 Amnion 18 10
7.5 22 13
8.0 26 16

Superscript numbers in table indicate references at the end of Chapter 4 .

* ±0.5 week age range for first visibility of each structure.



TABLE A-3

Approach to Gestational Age Assignment by Ultrasound on Initial Scan






































Stage of Pregnancy Basis for GA Accuracy (wks) *
First Trimester
Early (5-6 weeks) Sonographic milestones or MSD ±0.5
±0.5
Mid to late (6-13 weeks) CRL ±0.5-1.0
Second Trimester
If OFD measurable BPDc or HC ±1.2 (14-20 wks)
±1.9 (20-26 wks)
If OFD not measurable BPD or FL ±1.4 (14-20 wks)
±2.1-2.5 (20-26 wks)
Third Trimester
If OFD measurable BPDc, HC, or FL ±3.1-3.4 (26-32 wks)
±3.5-3.8 (32-42 wks)
If OFD not measurable FL ±3.1 (26-32 wks)
±3.5 (36-42 wks)

BPD, biparietal diameter; BPDc, corrected BPD; CRL, crown-rump length; FL, femur length; HC, head circumference; MSD, mean sac diameter; OFD, occipitofrontal diameter.

* Two standard deviations, or 95% confidence interval.



TABLE A-4

Variability in Predicting Menstrual Age From Sonographic Measurements (14-20 Weeks)
















































Parameter VARIABILITY (2 SD)
Hadlock et al * Rossavik and Fishburne Persson and Weldner Benson and Doubilet §
BPD 0.94 wk 1.02 wk 0.92 wk 1.40 wk
HC 0.84 wk 0.92 wk ND 1.20 wk
AC 1.04 wk 1.12 wk ND 2.10 wk
FL 0.96 wk ND 0.98 wk 1.40 wk
BPD, FL 0.80 wk ND 0.78 wk ND
HC, FL 0.76 wk ND ND ND

AC, abdominal circumference; BPD, biparietal diameter; FL, femur length; HC, head circumference; ND, no data.

* Data from Hadlock FP, Harrist RB, Martinez-Poyer J: How accurate is second trimester fetal dating? J Ultrasound Med 10:557, 1992.


Data from Rossavik IK, Fishburne JI: Conceptional age, menstrual age, and ultrasound age: a second trimester comparison of pregnancies of known conception date with pregnancies dated from the last menstrual period. Obstet Gynecol 73:243, 1989.


Data from Persson PH, Weldner BM: Reliability of ultrasound fetometry in estimating gestational age in the second trimester. Acta Obstet Gynecol Scand 65:481, 1986.


§ Data from Benson CB, Doubilet PM: Sonographic prediction of gestational age: accuracy of second and third trimester fetal measurements. Am J Roentgenol 157:1275, 1991.



TABLE A-5

Variability in Predicting Menstrual Age in the Second Half of Pregnancy (14-42 Weeks)

Adapted from Benson CB, Doubilet PM: Sonographic prediction of gestational age: accuracy of second and third trimester fetal measurements. Am J Roentgenol 157:1275, 1991.










































Parameter VARIABILITY IN WEEKS (±2 SD)
14-20 Weeks 20-26 Weeks 26-32 Weeks 32-42 Weeks
BPD 1.4 2.1 3.8 4.1
Corrected BPD 1.2 1.9 3.3 3.8
HC 1.2 1.9 3.4 3.8
AC 2.1 3.7 3.0 4.5
FL 1.4 2.5 3.1 3.5

AC, abdominal circumference; BPD, biparietal diameter; FL, femur length; HC, head circumference.


TABLE A-6

Variability Estimates for Secondary Biometric Parameters































































Parameter VARIABILITY IN WEEKS (±2 SD)
12-18 Weeks 18-24 Weeks 24-30 Weeks 30-36 Weeks 36-42 Weeks
Binocular distance * 1.8 2.4 3.0 4.0 4.0
Cerebellar diameter 1.0 1.8 2.0 2.4 3.2
Clavicle length 6.5 6.5 6.5 6.5 6.5
Radius length § 1.8 2.2 2.9 3.5 4.1
Ulna length || 3.6 3.6 3.6 3.6 3.6
Tibia length || 3.5 3.5 3.5 3.5 3.5
Foot length 1.2 1.7 2.2 2.6 3.1

* Data from Jeanty P, Cantraine F, Cousaert E, et al: The binocular distance: a new way to estimate fetal age. J Ultrasound Med 3:241, 1984.


Data from Hill LM: Transverse cerebellar diameter as a predictor of menstrual age. Obstet Gynecol 75:983, 1990.


Data from Yarkoni S, Schmidt W, Jeanty P, et al: Clavicular measurement: a new biometric parameter for fetal evaluation. J Ultrasound Med 4:467, 1985.


§ Data from Hill LM, Guzick D, Thomas ML, et al: Fetal radius length: a critical evaluation of race as a factor in gestational age assessment. Am J Obstet Gynecol 161:193, 1989.


|| Data from Jeanty P, Rodesch F, Delbeke D: Estimation of fetal age by long bone measurements. J Ultrasound Med 3:75, 1984.


Data from Mercer BM, Sklar S, Shariatmadar A, et al: Fetal foot length as a predictor of gestational age. Am J Obstet Gynecol 15:350, 1987.



TABLE A-7

Gestational Sac Measurement

From Hellman LM, Kobayashi M, Fillisti L, et al: Growth and development of the human fetus prior to the twentieth week of gestation. Am J Obstet Gynecol 103:789, 1969.











































































































































Mean Predicted Gestational Sac (cm) Gestational Age (wk) Mean Predicted Gestational Sac (cm) Gestational Age (wk)
1.0 5.0 3.6 8.8
1.1 5.2 3.7 8.9
1.2 5.3 3.8 9.0
1.3 5.5 3.9 9.2
1.4 5.6 4.0 9.3
1.5 5.8 4.1 9.5
1.6 5.9 4.2 9.6
1.7 6.0 4.3 9.7
1.8 6.2 4.4 9.9
1.9 6.3 4.5 10.0
2.0 6.5 4.6 10.2
2.1 6.6 4.7 10.3
2.2 6.8 4.8 10.5
2.3 6.9 4.9 10.6
2.4 7.0 5.0 10.7
2.5 7.2 5.1 10.9
2.6 7.3 5.2 11.0
2.7 7.5 5.3 11.2
2.8 7.6 5.4 11.3
2.9 7.8 5.5 11.5
3.0 7.9 5.6 11.6
3.1 8.0 5.7 11.7
3.2 8.2 5.8 11.9
3.3 8.3 5.9 12.0
3.4 8.5 6.0 12.2
3.5 8.6


TABLE A-8

Combined Data Comparing Menstrual Age With Mean Gestational Sac Diameter, Crown-Rump Length, and hCG Levels *














































































































































































































































































































































































































Menstrual Age (days) Menstrual Age (wk) Gestational Sac Size (mm) Crown-Rump Length (cm) HCG LEVEL (FIRST IRP)
Mean (U/L) Range (U/L)
30 4.3
31 4.4
32 4.6 3 1710 (1050-2800)
33 4.7 4 2320 (1440-3760)
34 4.9 5 3100 (1940-4980)
35 5.0 5.5 4090 (2580-6530)
36 5.1 6 5340 (3400-8450)
37 5.3 7 6880 (4420-10,810)
38 5.4 8 8770 (5680-13,660)
39 5.6 9 11,040 (7220-17,050)
40 5.7 10 0.2 13,730 (9050-21,040)
41 5.9 11 0.3 15,300 (10,140-23,340)
42 6.0 12 0.35 16,870 (11,230-25,640)
43 6.1 13 0.4 20,480 (13,750-30,880)
44 6.3 14 0.5 24,560 (16,650-36,750)
45 6.4 15 0.6 29,110 (19,910-43,220)
46 6.6 16 0.7 34,100 (25,530-50,210)
47 6.7 17 0.8 39,460 (27,470-57,640)
48 6.9 18 0.9 45,120 (31,700-65,380)
49 7.0 19 0.95 50,970 (36,130-73,280)
50 7.1 20 1.0 56,900 (40,700-81,150)
51 7.3 21 1.1 62,760 (45,300-88,790)
52 7.4 22 1.2 68,390 (49,810-95,990)
53 7.6 23 1.3 73,640 (54,120-102,540)
54 7.7 24 1.4 78,350 (58,100-108,230)
55 7.9 25 1.5 82,370 (61,640-112,870)
56 8.0 26 1.6 85,560 (64,600-116,310)
57 8.1 26.5 1.7
58 8.3 27 1.8
59 8.4 28 1.9
60 8.6 29 2.0
61 8.7 30 2.1
62 8.9 31 2.2
63 9.0 32 2.3
64 9.1 33 2.4
65 9.3 34 2.5
66 9.4 35 2.6
67 9.6 36 2.8
68 9.7 37 2.9
69 9.9 38 3.0
70 10.0 39 3.1
71 10.1 40 3.2
72 10.3 41 3.4
73 10.4 42 3.5
74 10.6 43 3.7
75 10.7 44 3.8
76 10.9 45 4.0
77 11.0 46 4.1
78 11.1 47 4.2
79 11.3 48 4.4
80 11.4 49 4.6
81 11.6 50 4.8
82 11.7 51 5.0
83 11.9 52 5.2
84 12.0 53 5.4

hCG, human chorionic gonadotropin; IRP, International Reference Preparation; U/L, units/liter.

Table appears in this form in Nyberg DA, Hill LM, Bohm-Velez M, et al: Transvaginal Ultrasound. St. Louis, Mosby-Year Book, 1992.

* Data from Daya S, Woods S: Transvaginal ultrasound scanning in early pregnancy and correlation with human chorionic gonadotropin levels. J Clin Ultrasound 19:139, 1991; Hadlock FP, Shah YP, Kanon DJ, et al: Fetal crown rump length: reevaluation of relation to menstrual age (5-18 weeks) with high-resolution real-time US. Radiology 182:501, 1992; and Robinson HP: “Gestation sac” volumes as determined by sonar in the first trimester of pregnancy. Br J Obstet Gynaecol 82:100, 1975.



TABLE A-9

Predicted Menstrual Age (MA) in Weeks From Crown-Rump Length (CRL) Measurements (cm) *

From Hadlock FP, Shah YP, Kanon DJ, et al: Fetal crown-rump length: reevaluation of relation to menstrual age (5-18 weeks) with high-resolution real-time US. Radiology 182:501, 1992.



































































































































































































































































































CRL MA CRL MA CRL MA
0.2 5.7 4.2 11.1 8.2 14.2
0.3 5.9 4.3 11.2 8.3 14.2
0.4 6.1 4.4 11.2 8.4 14.3
0.5 6.2 4.5 11.3 8.5 14.4
0.6 6.4 4.6 11.4 8.6 14.5
0.7 6.6 4.7 11.5 8.7 14.6
0.8 6.7 4.8 11.6 8.8 14.7
0.9 6.9 4.9 11.7 8.9 14.8
1.0 7.2 5.0 11.7 9.0 14.9
1.1 7.2 5.1 11.8 9.1 15.0
1.2 7.4 5.2 11.9 9.2 15.1
1.3 7.5 5.3 12.0 9.3 15.2
1.4 7.7 5.4 12.0 9.4 15.3
1.5 7.9 5.5 12.1 9.5 15.3
1.6 8.0 5.6 12.2 9.6 15.4
1.7 8.1 5.7 12.3 9.7 15.5
1.8 8.3 5.8 12.3 9.8 15.6
1.9 8.4 5.9 12.4 9.9 15.7
2.0 8.6 6.0 12.5 10.0 15.9
2.1 8.7 6.1 12.6 10.1 16.0
2.2 8.9 6.2 12.6 10.2 16.1
2.3 9.0 6.3 12.7 10.3 16.2
2.4 9.1 6.4 12.8 10.4 16.3
2.5 9.2 6.5 12.8 10.5 16.4
2.6 9.4 6.6 12.9 10.6 16.5
2.7 9.5 6.7 13.0 10.7 16.6
2.8 9.6 6.8 13.1 10.8 16.7
2.9 9.7 6.9 13.1 10.9 16.8
3.0 9.9 7.0 13.2 11.0 16.9
3.1 10.0 7.1 13.3 11.1 17.0
3.2 10.1 7.2 13.4 11.2 17.1
3.3 10.2 7.3 13.4 11.3 17.2
3.4 10.3 7.4 13.5 11.4 17.3
3.5 10.4 7.5 13.6 11.5 17.4
3.6 10.5 7.6 13.7 11.6 17.5
3.7 10.6 7.7 13.8 11.7 17.6
3.8 10.7 7.8 13.8 11.8 17.7
3.9 10.8 7.9 13.9 11.9 17.8
4.0 10.9 8.0 14.0 12.0 17.9
4.1 11.0 8.1 14.1 12.1 18.0

* The 95% confidence interval is ±8% of the predicted age.



TABLE A-11

Predicted Menstrual Age for Head Circumference Measurements (8.5-36.0 cm)

From Hadlock FP, Deter RL, Harrist RB, et al: Fetal head circumference: relation to menstrual age. AJR Am J Roentgenol 138:649, 1982.






















































































































































Head Circumference (cm) Menstrual Age (wk) Head Circumference (cm) Menstrual Age (wk)
8.5 13.7 22.5 24.4
9.0 14.0 23.0 24.9
9.5 14.3 23.5 25.4
10.0 14.6 24.0 25.9
10.5 15.0 24.5 26.4
11.0 15.3 25.0 26.9
11.5 15.6 25.5 27.5
12.0 15.9 26.0 28.0
12.5 16.3 26.5 28.6
13.0 16.6 27.0 29.2
13.5 17.0 27.5 29.8
14.0 17.3 28.0 30.3
14.5 17.7 28.5 31.0
15.0 18.1 29.0 31.6
15.5 18.4 29.5 32.2
16.0 18.8 30.0 32.8
16.5 19.2 30.5 33.5
17.0 19.6 31.0 34.2
17.5 20.0 31.5 34.9
18.0 20.4 32.0 35.5
18.5 20.8 32.5 36.3
19.0 21.2 33.0 37.0
19.5 21.6 33.5 37.7
20.0 22.1 34.0 38.5
20.5 22.5 34.5 39.2
21.0 23.0 35.0 40.0
21.5 23.4 35.5 40.8
22.0 23.9 36.0 41.6






















VARIABILITY ESTIMATES (±2 SD)
12-18 wk ±1.3 wk
18-24 wk ±1.6 wk
24-30 wk ±2.3 wk
30-36 wk ±2.7 wk
36-42 wk ±3.4 wk


TABLE A-12

Percentile Values for Fetal Head Circumference

Adapted from Hadlock FP, Deter RL, Harrist RB, et al: Estimating fetal age: computer-assisted analysis of multiple fetal growth parameters. Radiology 152:497, 1984.










































































































































































































Menstrual Weeks HEAD CIRCUMFERENCE (CM) BY PERCENTILE
3rd 10th 50th 90th 97th
14 8.8 9.1 9.7 10.3 10.6
15 10.0 10.4 11.0 11.6 12.0
16 11.3 11.7 12.4 13.1 13.5
17 12.6 13.0 13.8 14.6 15.0
18 13.7 14.2 15.1 16.0 16.5
19 14.9 15.5 16.4 17.4 17.9
20 16.1 16.7 17.7 18.7 19.3
21 17.2 17.8 18.9 20.0 20.6
22 18.3 18.9 20.1 21.3 21.9
23 19.4 20.1 21.3 22.5 23.2
24 20.4 21.1 22.4 23.7 24.3
25 21.4 22.2 23.5 24.9 25.6
26 22.4 23.2 24.6 26.0 26.8
27 23.3 24.1 25.6 27.1 27.9
28 24.2 25.1 26.6 28.1 29.0
29 25.0 25.9 27.5 29.1 30.0
30 25.8 26.8 28.4 30.0 31.0
31 26.7 27.6 29.3 31.0 31.9
32 27.4 28.4 30.1 31.8 32.8
33 28.0 29.0 30.8 32.6 33.6
34 28.7 29.7 31.5 33.3 34.3
35 29.3 30.4 32.2 34.1 35.1
36 29.9 30.9 32.8 34.7 35.8
37 30.3 31.4 33.3 35.2 36.3
38 30.8 31.9 33.8 35.8 36.8
39 31.1 32.2 34.2 36.2 37.3
40 31.5 32.6 34.6 36.6 37.7


TABLE A-13

Predicted Menstrual Age for Abdominal Circumference Measurements (10-36 cm)

From Hadlock FP, Deter RL, Harrist RB, et al: Fetal abdominal circumference as a predictor of menstrual age. AJR Am J Roentgenol 139:367, 1982.

















































































































































Abdominal Circumference (cm) Menstrual Age (wk) Abdominal Circumference (cm) Menstrual Age (wk)
10.0 15.6 23.5 27.7
10.5 16.1 24.0 28.2
11.0 16.5 24.5 28.7
11.5 16.9 25.0 29.2
12.0 17.3 25.5 29.7
12.5 17.8 26.0 30.1
13.0 18.2 26.5 30.6
13.5 18.6 27.0 31.1
14.0 19.1 27.5 31.6
14.5 19.5 28.0 32.1
15.0 20.0 28.5 32.6
15.5 20.4 29.0 33.1
16.0 20.8 29.5 33.6
16.5 21.3 30.0 34.1
17.0 21.7 30.5 34.6
17.5 22.2 31.0 35.1
18.0 22.6 31.5 35.6
18.5 23.1 32.0 36.1
19.0 23.6 32.5 36.6
19.5 24.0 33.0 37.1
20.0 24.5 33.5 37.6
20.5 24.9 34.0 38.1
21.0 25.4 34.5 38.7
21.5 25.9 35.0 39.2
22.0 26.3 35.5 39.7
22.5 26.8 36.0 40.2
23.0 27.3






















VARIABILITY ESTIMATES (±2 SD)
12-18 wk ±1.9 wk
18-24 wk ±2.0 wk
24-30 wk ±2.2 wk
30-36 wk ±3.0 wk
36-42 wk ±2.5 wk


TABLE A-14

Percentile Values for Fetal Abdominal Circumference

Adapted from Hadlock FP, Deter RL, Harrist RB, et al: Estimating fetal age: computer-assisted analysis of multiple fetal growth parameters. Radiology 152:497, 1984.










































































































































































































Menstrual Age (Wks) ABDOMINAL CIRCUMFERENCE (CM) BY PERCENTILE
3rd 10th 50th 90th 97th
14 6.4 6.7 7.3 7.9 8.3
15 7.5 7.9 8.6 9.3 9.7
16 8.6 9.1 9.9 10.7 11.2
17 9.7 10.3 11.2 12.1 12.7
18 10.9 11.5 12.5 13.5 14.1
19 11.9 12.6 13.7 14.8 15.5
20 13.1 13.8 15.0 16.3 17.0
21 14.1 14.9 16.2 17.6 18.3
22 15.1 16.0 17.4 18.8 19.7
23 16.1 17.0 18.5 20.0 20.9
24 17.1 18.1 19.7 21.3 22.3
25 18.1 19.1 20.8 22.5 23.5
26 19.1 20.1 21.9 23.7 24.8
27 20.0 21.1 23.0 24.9 26.0
28 20.9 22.0 24.0 26.0 27.1
29 21.8 23.0 25.1 27.2 28.4
30 22.7 23.9 26.1 28.3 29.5
31 23.6 24.9 27.1 29.4 30.6
32 24.5 25.8 28.1 30.4 31.8
33 25.3 26.7 29.1 31.5 32.9
34 26.1 27.5 30.0 32.5 33.9
35 26.9 28.3 30.9 33.5 34.9
36 27.7 29.2 31.8 34.4 35.9
37 28.5 30.0 32.7 35.4 37.0
38 29.2 30.8 33.6 36.4 38.0
39 29.9 31.6 34.4 37.3 38.9
40 30.7 32.4 35.3 38.2 39.9


TABLE A-15

A Comparison of Abdominal Circumference Percentiles Using Sonography

















































































































Menstrual Age (wk) ABDOMINAL CIRCUMFERENCE (cm)
10th PERCENTILE 90th PERCENTILE
Jeanty et al * Hadlock et al Tamura and Sabbagha Jeanty et al * Hadlock et al Tamura and Sabbagha
18 10.2 11.5 11.7 13.6 13.5 12.0
20 12.4 13.7 14.2 15.8 16.3 16.7
22 14.6 16.0 14.7 18.0 18.8 19.7
24 16.7 18.1 18.9 20.1 21.3 22.8
26 18.8 20.1 19.8 22.2 23.7 26.7
28 20.8 22.0 23.1 24.2 26.0 27.2
30 22.7 23.9 24.4 26.1 28.3 30.1
32 24.5 25.8 26.7 27.9 30.4 32.4
34 26.2 27.5 28.6 29.6 32.5 33.6
36 27.6 29.2 31.0 31.0 34.4 37.8
38 28.9 30.8 32.8 32.3 36.4 38.5
40 29.9 32.4 33.3 33.3 38.2 41.2

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Nov 8, 2019 | Posted by in GYNECOLOGY | Comments Off on Measurements Frequently Used to Estimate Gestational Age and Fetal Biometry

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