Document Detail

New crown-rump length curve based on over 3500 pregnancies.
MedLine Citation:
PMID:  20512816     Owner:  NLM     Status:  MEDLINE    
OBJECTIVES: The Robinson and Hadlock crown-rump length (CRL) curves are commonly used to estimate gestational age (GA) based on the CRL of an embryo or fetus. However, the Robinson curve was derived from a small population using transabdominal sonography and the Hadlock curve was generated using early transvaginal ultrasound equipment. The aim of this study was to use transvaginal and transabdominal ultrasound to study a large population of early pregnancies to assess embryonic or fetal size, and so create a new normal CRL curve from 5.5 weeks' gestation. We compared this with the Robinson and Hadlock CRL curves.
METHODS: A retrospective database study of CRL in first-trimester embryos was conducted in a fetal medicine referral center with a predominantly Caucasian population. Linear mixed-effects analysis was performed to determine the relationship between CRL and GA. After internal validation of this curve, the CRL was compared with the expected CRL at a given GA according to both the Robinson and Hadlock models based on the paired t-test. Bland-Altman plots were constructed to compare the CRL measurements obtained in our study population with those predicted according to GA by both the Robinson and Hadlock curves.
RESULTS: In total 3710 normal singleton pregnancies with a known last menstrual period were included in the study, corresponding to 4387 scans. Our data differed significantly from both the Robinson and the Hadlock curves (paired t-test, P < 0.0001). A mixed-effects model for CRL as a function of GA was developed on 70% of the data and internally validated with z-scores on the remaining 30%. The new curve extended from 5.5 to 14 weeks' gestation. Compared to our CRL curve, the Robinson curve gave a 4-day underestimation of GA at 6 weeks with a difference in CRL of 3.7 mm and a 1-day overestimation from 11 to 14 weeks with a difference in CRL of 0.9-1 mm. A comparison between our curve and the Hadlock curve showed a difference in CRL of 2.7 mm at 6 weeks, equivalent to an underestimation of 3 days, and a difference in CRL of 4.8 mm at 14 weeks, equivalent to an overestimation of 2 days. At 9 weeks all three curves were similar.
CONCLUSION: The new CRL curve suggests differences in the range of CRL measurements compared with the Robinson and Hadlock curves. These differences are most significant at the beginning and the end of the first trimester, and may lead to more accurate estimations of GA.
A Pexsters; A Daemen; C Bottomley; D Van Schoubroeck; L De Catte; B De Moor; T D'Hooghe; C Lees; D Timmerman; T Bourne
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't; Validation Studies    
Journal Detail:
Title:  Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology     Volume:  35     ISSN:  1469-0705     ISO Abbreviation:  Ultrasound Obstet Gynecol     Publication Date:  2010 Jun 
Date Detail:
Created Date:  2010-06-07     Completed Date:  2010-12-07     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9108340     Medline TA:  Ultrasound Obstet Gynecol     Country:  England    
Other Details:
Languages:  eng     Pagination:  650-5     Citation Subset:  IM    
Department of Obstetrics and Gynecology, University Hospitals, Katholieke Universiteit Leuven, Leuven, Belgium.
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MeSH Terms
Crown-Rump Length*
Gestational Age
Menstrual Cycle / physiology*
Pregnancy Trimester, First / physiology*
Reference Values
Retrospective Studies
Ultrasonography, Prenatal / instrumentation,  methods*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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