CRL

• Timing of ovulation
• Measurement error
• Biologic variation

• 416 patients
• 5 to 19.7 weeks
• Transbdominal and transvaginal

• Midline sagittal section
• Horizontal orientation
• Genital tubercle/fetal spine visible
• Measure maxium unflexed length
• Best of three measurements
• Greater than or equal to 7 weeks

• 143 patients
• Measurements between 1 and 25 mm
• "Greatest length"
• GA (days) = EES + 42

• 3710 singleton pregnancies
• Known LMP
• 5.5 to 14 weeks' gestation
• New CRL curve compared to Robinson & Hadlock
• 96% of scans before 10 weeks transvaginal

1. Robinson HP, Fleming JE. A critical evaluation of sonar "crown-rump length" measurements. Br J Obstet Gynaecol. 1975a;82:702-710.

2. American Institute of Ultrasound in Medicine. AIUM practice guideline for the performance of obstetric ultrasound examinations. J Ultrasound Med. 2010b;29:157-166.

3. Hearn JP, Webley GE, Gidley-Baird AA. Chorionic gonadotrophin and embryo-maternal recognition during the peri-implantation period in primates. J Reprod Fertil. 1991c;92:497-509.

4. Salomon LJ. Early fetal growth: concepts and pitfalls. Ultrasound Obstet Gynecol. 2010d;35:385-389.

5. Hadlock FP, Shah YP, Kanon DJ, Lindsey JV. Fetal crown-rump length: reevaluation of relation to menstrual age (5-18 weeks) with high-resolution real-time US. Radiology. 1992e;182:501-505.

6. Loughna P, Chitty L, Evans T, Chudleigh T. Fetal Size and Dating: Charts Recommended for Clinical Obstetric Practice. Ultrasound. f;17:160-166.

7. Pilu G. The global library of women's medicine; Available from: http://www.glowm.com/?p=glowm.cml/ultrasoundAtlas.

8. Salomon LJ, Cavicchioni O, Bernard JP, Duyme M, Ville Y. Growth discrepancy in twins in the first trimester of pregnancy. Ultrasound Obstet Gynecol. 2005a;26:512-516.

9. Kagan KO, Hoopmann M, Baker A, Huebner M, Abele H, Wright D. Impact of bias in crown-rump length measurement at first-trimester screening for trisomy 21. Ultrasound Obstet Gynecol. 2012b;40:135-139.

10. Mahendru A, Daemen A, Everett T, et al. Impact of ovulation and implantation timing on first trimester crown-rump length and gestational age. Ultrasound Obstet Gynecol. 2012c.

11. Verburg BO, Mulder PG, Hofman A, Jaddoe VW, Witteman JC, Steegers EA. Intra- and interobserver reproducibility study of early fetal growth parameters. Prenat Diagn. 2008d;28:323-331.

12. Verburg BO, Steegers EA, De Ridder M, et al. New charts for ultrasound dating of pregnancy and assessment of fetal growth: longitudinal data from a population-based cohort study. Ultrasound Obstet Gynecol. 2008e;31:388-396.

13. Pexsters A, Daemen A, Bottomley C, et al. New crown-rump length curve based on over 3500 pregnancies. Ultrasound Obstet Gynecol. 2010f;35:650-655.

14. Papaioannou GI, Syngelaki A, Poon LC, Ross JA, Nicolaides KH. Normal ranges of embryonic length, embryonic heart rate, gestational sac diameter and yolk sac diameter at 6-10 weeks. Fetal Diagn Ther. 2010g;28:207-219.

15. Mook-Kanamori DO, Steegers EA, Eilers PH, Raat H, Hofman A, Jaddoe VW. Risk factors and outcomes associated with first-trimester fetal growth restriction. JAMA. 2010h;303:527-534.

16. Robinson HP. Sonar measurement of fetal crown-rump length as means of assessing maturity in first trimester of pregnancy. Br Med J. 1973i;4:28-31.

17. Bromley B, Shipp TD, Benacerraf BR. Structural anomalies in early embryonic death: a 3-dimensional pictorial essay. J Ultrasound Med. 2010j;29:445-453.

18. Wilcox AJ, Baird DD, Weinberg CR. Time of implantation of the conceptus and loss of pregnancy. N Engl J Med. 1999k;340:1796-1799.

19. Delpachitra P, Palmer K, Onwude J, et al. Ultrasound Reference Chart Based on IVF Dates to Estimate Gestational Age at 6-9 weeks' Gestation. ISRN Obstet Gynecol. 2012l;2012:938583.

20. Goldstein SR, Wolfson R. Endovaginal ultrasonographic measurement of early embryonic size as a means of assessing gestational age. J Ultrasound Med. 1994;13:27-31.

Bourne 2012

• Preterm birth
• IUGR
• Low birth weight

• 101 pregnancies
• Established ovulation and implantation with urinary LH and hCG
• Studied relationship between fetal size, ovulation and implantation

Crown Rump Length

Factors Affecting Fetal Size

• Equipment
• Technical skill
• CRL tables
• Advanced maternal age
• High blood pressure
• Low Hematocrit
• Smoking
• Folic acid deficiency

Bourne 2010

A Lot about a little

6

7

9

Goldstein 1994

GA (weeks) = CRL (cm) + 6.5

Hadlock 1992

• Origins
• Method
• Current Information
• Factors