[Comparison of duplex systems and simple Doppler equipment in obstetric diagnosis]

Duplex systems are normally used in obstretric Doppler sonography. The fact that these systems are technically complex and very costly to some extent contradicts the use of Doppler sonography as a screening method. This study examines whether simplex Doppler systems without tomographic imaging and not involving costly technology, such as frequency analysis, are as suitable for Doppler examination in pregnancy as the costly duplex systems. Examinations of 83 patients between GW 32 and 42 showed that both the umbilical and uterine arteries can be reliably identified using the simplex Doppler unit. A comparison of Doppler curves obtained with duplex and simplex Doppler systems showed that the two devices produced the same results. The Doppler curves were compared both as regards their geometry, according to the score described by Fendel et al. (1988), as well as on the basis of calculated parameters. The scores were correlated to delivery mode and birth weight. However, the fetal aorta cannot be reliably located with the simplex Doppler unit unless it has been tomographically imaged beforehand. Doppler examination of the umbilical and uterine arteries provides the best information for selection of high-risk pregnancies. It therefore appears sufficient to screen patients with the simplex Doppler described here and to perform more detailed diagnostic investigations with a duplex systems in the event of pathologic findings.