Lee, W., T. Riggs, et al. (2010). "Fetal echocardiography: z-score reference ranges for a large patient population." __Ultrasound Obstet Gynecol__ **35**(1): 28-34.

Ultrasound Obstet Gynecol 2010; 35: 28–34
Published online 15 December 2009 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/uog.7483

Fetal echocardiography: z-score reference ranges for a large patient population

W. LEE*, T. RIGGS†‡, V. AMULA†, M. TSIMIS§, N. CUTLER†, R. BRONSTEEN* and C. H. COMSTOCK*

*Department of Obstetrics and Gynecology, William Beaumont Hospital, †Department of Pediatrics, Beaumont Children's Hospital and ‡Division of Biostatistics, Beaumont Research Institute, Royal Oak and §Wayne State University School of Medicine, Detroit, MI, USA

ABSTRACT

OBJECTIVES: The main goal was to develop new z-score
reference ranges for common fetal echocardiographic
measurements from a large referral population.

METHODS: A retrospective cross-sectional study of 2735
fetuses was performed for standard biometry (biparietal
diameter (BPD) and femoral diaphysis length (FDL)) and
an assessment of menstrual age (MA). Standardized fetal
echocardiographic measurements included aortic valve
annulus and pulmonary valve annulus diameters at endsystole,
right and left ventricular diameters at end-diastole,
and cardiac circumference from a four-chamber view of
the heart during end-diastole. Normal z-score ranges were
developed for these echocardiographic measurements
using MA, BPD and FDL as independent variables.
This was accomplished by using first standard regression
analysis and then weighted regression of absolute residual
values for each parameter in order to adjust for inconstant
variance.

RESULTS: A simple, linear regression model was the best
description of the data in each case and correlations
between fetal cardiac measurements and the independent
variables were excellent. There was significant
heteroscedasticity of standard deviation with increasing
gestational age, which also could be modeled with simple
linear regression. After this adjustment, the residuals conformed
to a normal distribution, validating the calculation
and interpretation of z-scores.

CONCLUSION: Development of reliable z-scores is possible
for common fetal echocardiographic parameters by
applying statistical methods that are based on a large
sample size and weighted regression of absolute residuals
in order to minimize the effect of heteroscedasticity.
These normative ranges should be especially useful for the
detection and monitoring of suspected fetal cardiac size
and growth abnormalities. Copyright 2009 ISUOG.
Published by John Wiley & Sons, Ltd.