Errors and artifacts encountered in the monitoring of fetal respiratory movements using untrasound.

A study is described of the possible sources of error and artifact arising in the monitoring of fetal respiratory movements using ultrasound, and their effect upon the clinical usefulness of the technique.Major artifacts arose from attempts to use the instrument controls to compensate for a poor choice of insonation direction, and from the use of a belt-mounted transducer.Critical requirements of the necessary instrumentation are discussed, together with the limitations of commercially-available equipment.