Abstract
The present data, obtained from chronically instrumented fetal lambs, includes three fetuses monitored throughout spontaneous labour, six fetuses with spontaneously developed long-term ST waveform changes and another three fetuses which died in the post-operative period. Uterine contractions could by themselves cause an increase in T wave height (T/QRS ratio>0.30). If the ST elevation was normalised between contractions the fetus seemed to compensate to a moderate degree of hypoxia. When oxygenation was further reduced the T wave remained elevated between contractions and a progressive increase occurred in the T/QRS ratio (>0.60) during the final stages of labour, in parallel with increasing blood lactate levels. Death in utero, whatever the cause (bleeding, infection or spontaneous hypoxia), was always preceded by marked ST waveform changes. It is concluded that ST elevation with high peaked T waves can appear on a long-term basis in fetuses with intrauterine complications.