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

• Published in: Ultrasound in obstetrics & gynecology Vol. 35; no. 1; pp. 28 - 34
• Main Authors: Lee, W., Riggs, T., Amula, V., Tsimis, M., Cutler, N., Bronsteen, R., Comstock, C. H.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.01.2010; Wiley
• Subjects: Adolescent; Adult; Age; Aortic valve; Biological and medical sciences; biometry; Biometry - methods; Cardiovascular system; Cross-Sectional Studies; Data processing; Diaphysis; Echocardiography; Female; Femur; Fetal Diseases - diagnostic imaging; fetal echocardiography; Fetal Heart - diagnostic imaging; fetal measurements; Fetuses; Gestational Age; Gynecology; Gynecology. Andrology. Obstetrics; Heart; Humans; Investigative techniques, diagnostic techniques (general aspects); Linear Models; Lung; Medical sciences; Menstruation; Obstetrics; Population Groups; Pregnancy; Reference Values; Regression analysis; Retrospective Studies; Standard deviation; Statistics; Ultrasonic investigative techniques; Ultrasonography, Prenatal - classification; Ultrasonography, Prenatal - methods; Ultrasound; Ventricle; Young Adult; z‐scores; Sonography; Pregnancy; Human; biometry; Echocardiography; Gynecology; Reference; z-scores; Fetus; fetal echocardiography; Obstetrics; fetal measurements
• ISSN: 0960-7692; 1469-0705; 1469-0705
• DOI: 10.1002/uog.7483

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 end‐systole, 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.