Alterations in the electrocardiogram of the fetal lamb as a sign of fetal asphyxia. A comparison between the scalp lead and the precordial lead.

Progressive changes in the ST-T period of the fetal electrocardiogram (FECG) were studied in 18 lamb fetuses, acutely exteriorized and subjected to graded hypoxia. The aim of the study was to compare the bipolar precordial lead (CR-lead) with the unipolar scalp lead, and to correlate the alterations in the FECG to blood-gas and acid-base status. The scalp lead gave less information regarding fetal condition and was more difficult to interpret than the precordial lead. This might be one factor in the controversy regarding the significance of alterations in the FECG during asphyxia and labor, since the scalp lead is used mainly in clinical situations. Our previous results demonstrating progressive changes in the ST-T period of the FECG during hypoxia in experimental animals and showing the same ECG changes in newborn human infants immediately after birth, were registered with the bipolar precordial lead. It is possible that a bipolar scalp lead might give more information regarding the fetal condition than the unipolar scalp lead mainly used in clinical practice.