Objective: Our purpose was to develop an ultrasonographic method of using multiple electronic calipers for on-screen measurement of fetal cardiac axis.
Study design: Two hundred low-risk patients who were seen for antenatal ultrasonography were studied. Standard biometry, anatomic survey, and echocardiography were performed on all fetuses. By use of a four-chamber view fetal cardiac axis was measured with electronic calipers. A table, derived from a trigonometric formula, was created to convert the caliper measurements to cardiac axis in degrees. The results were compared with a protractor-determined fetal cardiac axis.
Results: All echocardiograms had normal results. Fetal cardiac axis (+/- 2 SD) by the ultrasonographic method was 43 degrees (+/- 16 degrees) versus 43 degrees (+/- 14 degrees) by the protractor method. This difference was not significant.
Conclusion: An on-screen method to determine fetal cardiac axis by use of multiple calipers is described. It is comparable to a protractor-measured fetal cardiac axis.