Noninvasive fetal electrocardiography following intermittent umbilical cord occlusion in the preterm ovine fetus

OBJECTIVE: To investigate whether a noninvasive fetal electrocardiography (fECG) system can identify cardiovascular responses to fetal hypoxaemia and validate the results using standard invasive fECG monitoring techniques. DESIGN: Prospective cohort study. SETTING: Biological research facilities at The University of Southampton. POPULATION OR SAMPLE: Late gestation ovine fetuses; n = 5. METHODS: Five fetal lambs underwent implantation of vascular catheters, umbilical cord occluder and invasive ECG chest electrodes under general anaesthesia (3% halothane/O(2)) at 119 days of gestation (term approximately 147 days of gestation). After 5 days of recovery blood pressure, blood gases, glucose and pH were monitored. At 124 and 125 days of gestation following a 10-minute baseline period a 90-second cord occlusion was applied. Noninvasive fetal ECG was recorded from maternal transabdominal electrodes using advanced signal-processing techniques, concurrently with invasive fECG recordings. MAIN OUTCOME MEASURES: Comparison of T:QRS ratios of the ECG waveform from noninvasive and invasive fECG monitoring systems. RESULTS: Our fECG monitoring system is able to demonstrate changes in waveforms during periods of hypoxaemia similar to those obtained invasively, which could indicate fetal distress. CONCLUSIONS: These findings may indicate a future use for noninvasive electrocardiography during human fetal monitoring both before and during labour in term and preterm pregnancies.