Clinical Fetal Electrocardiography. Its Practical Accomplishment

The recording of the electrocardiogram of the human fetus in utero, although long attempted (Cremer, 1 Foá 2 ), has been only indifferently successful even late in pregnancy. 3 , 4 , 5 We have developed a technic of definite clinical value by using a single stage resistance-coupled amplifier (successfully employed 6 on the embryo chick heart) with a conventional portable electrocardiograph. The baseline of the tracing was stabilized by means of series condensers of 0.001 to 0.05 microfarads capacities which were coupled to the lead wire when needed for damping the respiratory artefacts of the mother. The fetal heart potentials, picked up by disc electrodes on the pregnant subject's abdomen (xiphoid-pubis application to minimize the pickup of the maternal electrocardiogram) were amplified 20 times, thereby bringing the fetal electrocardiogram into plain view while keeping that of the mother within the limits of recording of the apparatus. The amplifier measures 9 × 5 × 7 inches, weighs 12 pounds, is constructed of standard radio parts, is simple to operate, and together with the electrocardiograph makes an easily portable device. With this technic we are able to record the action current of the fetal heart in virtually all instances during the last 2 months of pregnancy, usually in the sixth and seventh month, and frequently in the fourth and fifth month. Fig. 1 illustrates a typical result, and Fig. 2 shows one of our best. As is obvious from the illustrations, the baseline irregularity is the present limiting factor, for it tends to obscure the characteristically small fetal electrocardiogram of early pregnancy. These artefacts single stage resistance-coupled amplifier (successfully employed 6 on the embryo chick heart) with a conventional portable electrocardiograph. The baseline of the tracing was stablized by means of series condensers of 0.001 to 0.05 microfarads capacities which were coupled to the lead wire when needed for damping the respiratory artefacts of the mother.