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BJOG. 2014 Apr;121(5):556-65. doi: 10.1111/1471-0528.12478. Epub 2014 Jan 6.

Pregnancy dating by fetal crown-rump length: a systematic review of charts.

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1
Nuffield Department of Obstetrics & Gynaecology, University of Oxford, Oxford, UK.

Abstract

BACKGROUND:

Fetal crown-rump length (CRL) measurement by ultrasound in the first trimester is the standard method for pregnancy dating; however, a multitude of CRL equations to estimate gestational age (GA) are reported in the literature.

OBJECTIVE:

To evaluate the methodological quality used in studies reporting CRL equations to estimate GA using a set of predefined criteria.

SEARCH STRATEGY:

Searches of MEDLINE, EMBASE, and CINAHL databases, from 1948 to 31 January 2011, and secondary reference sources, were performed.

SELECTION CRITERIA:

Observational ultrasound studies, where the primary aim was to create equations for GA estimation using a CRL measurement.

DATA COLLECTION AND ANALYSIS:

Included studies were scored against predefined independently agreed methodological criteria: an overall quality score was calculated for each study.

MAIN RESULTS:

The searches yielded 1142 citations. Two reviewers screened the papers and independently assessed the full-text versions of 29 eligible studies. The highest potential for bias was noted in inclusion and exclusion criteria, and in maternal demographic characteristics. No studies had systematic ultrasound quality-control measures. The four studies with the highest scores (lowest risk of bias) satisfied 18 or more of the 29 criteria; these showed lower variation in GA estimation than the remaining, lower-scoring studies. This was particularly evident at the extremes of GA.

AUTHOR'S CONCLUSIONS:

Considerable methodological heterogeneity and limitations exist in studies reporting CRL equations for estimating GA, and these result in a wide range of estimated GAs for any given CRL; however, when studies with the highest methodological quality are used, this range is reduced.

KEYWORDS:

Crown-rump length; dating chart; gestational age; pregnancy dating; ultrasound

PMID:
24387345
DOI:
10.1111/1471-0528.12478
[Indexed for MEDLINE]
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