Correction of systematic bias in ultrasound dating in studies of small-for-gestational-age birth: an example from the Iowa Health in Pregnancy Study

Karisa K Harland; Audrey F Saftlas; Anne B Wallis; Jerome Yankowitz; Elizabeth W Triche; M Bridget Zimmerman

doi:10.1093/aje/kws120

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Correction of systematic bias in ultrasound dating in studies of small-for-gestational-age birth: an example from the Iowa Health in Pregnancy Study

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Correction of systematic bias in ultrasound dating in studies of small-for-gestational-age birth: an example from the Iowa Health in Pregnancy Study

Karisa K Harland, Audrey F Saftlas, Anne B Wallis, Jerome Yankowitz, Elizabeth W Triche and M Bridget Zimmerman

American journal of epidemiology, Vol.176(5), pp.443-455

09/01/2012

DOI: 10.1093/aje/kws120

PMCID: PMC3499119

PMID: 22886591

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Abstract

The authors examined whether early ultrasound dating (≤20 weeks) of gestational age (GA) in small-for-gestational-age (SGA) fetuses may underestimate gestational duration and therefore the incidence of SGA birth. Within a population-based case-control study (May 2002-June 2005) of Iowa SGA births and preterm deliveries identified from birth records (n = 2,709), the authors illustrate a novel methodological approach with which to assess and correct for systematic underestimation of GA by early ultrasound in women with suspected SGA fetuses. After restricting the analysis to subjects with first-trimester prenatal care, a nonmissing date of the last menstrual period (LMP), and early ultrasound (n = 1,135), SGA subjects' ultrasound GA was 5.5 days less than their LMP GA, on average. Multivariable linear regression was conducted to determine the extent to which ultrasound GA predicted LMP dating and to correct for systematic misclassification that results after applying standard guidelines to adjudicate differences in these measures. In the unadjusted model, SGA subjects required a correction of +1.5 weeks to the ultrasound estimate. With adjustment for maternal age, smoking, and first-trimester vaginal bleeding, standard guidelines for adjudicating differences in ultrasound and LMP dating underestimated SGA birth by 12.9% and overestimated preterm delivery by 8.7%. This methodological approach can be applied by researchers using different study populations in similar research contexts.

Multivariate Analysis

Data Interpretation, Statistical

Bias

Humans

Linear Models

Male

Gestational Age

Case-Control Studies

Pregnancy

Iowa

Ultrasonography, Prenatal

Adult

Female

Infant, Small for Gestational Age

Infant, Newborn

Details

Title: Subtitle: Correction of systematic bias in ultrasound dating in studies of small-for-gestational-age birth: an example from the Iowa Health in Pregnancy Study
Creators: Karisa K Harland - Injury Prevention Research Center and Department of Epidemiology, University of Iowa, Iowa City, IA 52242-5000, USA. kari-harland@uiowa.edu
Audrey F Saftlas
Anne B Wallis
Jerome Yankowitz
Elizabeth W Triche
M Bridget Zimmerman
Resource Type: Journal article
Publication Details: American journal of epidemiology, Vol.176(5), pp.443-455
DOI: 10.1093/aje/kws120
PMID: 22886591
PMCID: PMC3499119
NLM abbreviation: Am J Epidemiol
ISSN: 0002-9262
eISSN: 1476-6256
Publisher: United States
Grant note: R49 CD001167 / ODCDC CDC HHS R49 CE001167 / NCIPC CDC HHS R01-HD39753 / NICHD NIH HHS R01 HD039753 / NICHD NIH HHS
Language: English
Date published: 09/01/2012
Academic Unit: Epidemiology; Emergency Medicine; Biostatistics; Obstetrics and Gynecology; Injury Prevention Research Center; Public Policy Center (Archive); Law Faculty
Record Identifier: 9983997463802771

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