Technic and results of routine fetal electrocardiography during pregnancy

Abstract

The principles on which the routine technic of fetal electrocardiography has been developed are use of the electrocardiographic apparatus without modification, application of electrodes to the extremities only, increase of the amplitude of waves and decrease of the fuzziness of tracings by simple means. The technic of obtaining and interpreting fetal electrocardiograms is described in detail. The difference between the results obtained by use of the usual technic and those obtained by use of special technic is illustrated in Figs. 1 to 3.Seventy fetal electrocardiograms were recorded from 52 patients during the last seventy days of pregnancy. Sixty-one or 87 per cent of the electrocardiograms were positive and 9 or 13 per cent were negative. During the last twenty days of pregnancy 40 out of 44 electrocardiograms or 91 per cent were positive. Between the twenty-first and seventieth day before delivery 21 out of 26 electrocardiograms or 81 per cent were positive. In cases of vertex presentation, during the last twenty days of pregnancy, 94 per cent of the electrocardiograms were positive and, between the twenty-first and seventieth days before delivery, 87 per cent were positive.Besides the usual Leads I, II and III, two more leads were used (right arm—right thigh; left arm—right thigh). The largest number of positive results were obtained in the third lead (46) and in the fifth lead (left arm—right thigh) (45) because they are most favorable in the left vertex position of the fetus which is the most frequent position.Twenty-five per cent of the positive fetal electrocardiograms were positive in only one lead, 31 per cent in two leads, 15 per cent in three leads and 29 per cent in four leads. In the last three weeks before delivery, 38 per cent of the tests were positive in four leads.As an example of the practical value of the fetal electrocardiogram, a case is described and the electrocardiogram is shown in which the fetal heart tones could not be heard through the stethoscope and the electrocardiogram gave evidence of a living fetus fifty-five, forty-three, and thirty-one days before the expected term.Fetal electrocardiography in pregnancy and labor gives objective graphic evidence regarding the viability of the fetus. This is of practical value in doubtful cases in which the older subjective methods, stethoscopic examiantion, and observation of fetal movements fail. By means of the technic presented, the rate, rhythm, and regularity of fetal heart action can be observed in the electrocardiogram. The scientific field of fetal electrocardiography might even be wider. Such a procedure renders possible observation of the fetus objectively under various conditions in pregnancy and labor. The relationship between maternal and fetal heart action can be easily studied.