Journal of Ultrasound in Medicine, Vol 12, Issue 11 659-663, Copyright © 1993 by American Institute of Ultrasound in Medicine
Fetal echocardiography: factors that influence imaging of the fetal heart during the second trimester of pregnancy
G. R. DeVore, A. L. Medearis, M. B. Bear, J. Horenstein and L. D. Platt
Genetics Institute Fetal Diagnostic Center, Pasadena, California.
OBJECTIVE. The four-chamber view of the heart is an important component of
the ultrasonographic examination of the fetus. However, during the second
trimester of pregnancy the fetal heart cannot always be imaged in every
patient. The purpose of this study was to ascertain the rate of successful
imaging of the fetal heart during the second trimester and to determine
factors that may influence imaging. METHODS. Seven hundred and nine second
trimester fetuses were examined and an attempt was made to obtain the
four-chamber and outflow tract views of the heart. Analysis included
multiple logistic regression models of the main effects and interactions of
ten candidate variables. RESULTS. The four chambers and outflow tracts were
imaged in 643 fetuses (90.7%) and not imaged in 66 (9.3%). Fifty-two of 709
patients (7.3%) had had previous surgery. In the 52 patients with a history
of previous surgery, the heart could not be imaged in 18 (34%). Six hundred
and fifty-seven patients (92.7%) did not have previous surgery. Of this
group, the fetal heart could not be imaged in 48 (7.3%). In only one fetus
in which the heart could not be imaged was it because of fetal position.
Three independent risk factors that influenced imaging of the fetal heart
were gestational age, maternal adipose tissue thickness, and previous lower
abdominal surgery. Increasing gestational age increased the probability of
imaging the heart, whereas increasing adipose tissue thickness and a
history of previous surgery decreased the probability of imaging the heart.
COMMENTS. When the fetal heart cannot be imaged during the second
trimester, these factors should be identified. Using data from this study,
the gestational age at which the highest probability of imaging the heart
can be determined if the thickness of the adipose tissue and a history of
lower abdominal surgery are known.