TABLE A-1
Methods for Determining Menstrual Age
| 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.
Adapted from Frank P. Hadlock, MD, and James D. Bowie, MD.
* 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.
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)
| 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.
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.
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
| 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 |
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.
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) *
| 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 |
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.
TABLE A-11
Predicted Menstrual Age for Head Circumference Measurements (8.5-36.0 cm)
| 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 |
From Hadlock FP, Deter RL, Harrist RB, et al: Fetal head circumference: relation to menstrual age. AJR Am J Roentgenol 138:649, 1982.
TABLE A-12
Percentile Values for Fetal Head Circumference
| 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 |
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.
TABLE A-13
Predicted Menstrual Age for Abdominal Circumference Measurements (10-36 cm)
| 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 |
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.
TABLE A-14
Percentile Values for Fetal Abdominal Circumference
| 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 |
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.
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 |
* Adapted from Jeanty P, Cousaert E, Cantraine F: Normal growth of the abdominal perimeter. Am J Perinatol 1:129, 1984.
‡ 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.
† Adapted from Tamura RK, Sabbagha RE: Percentile ranks of sonar fetal abdominal circumference measurements. Am J Obstet Gynecol 138:475, 1980.
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