Determination of the presence of fetal apnoea using umbilical artery and umbilical vein Doppler waveforms.

Fetal breathing movements were observed using real-time ultrasound imaging. Simultaneous Doppler recordings of the flow velocity waveform from the umbilical artery and umbilical vein were obtained. Twenty patients were studied. The Doppler traces obtained during fetal apnoea and fetal breathing for each patient were analysed using a BBC microcomputer. A combination of venous variation index (VVI) and the coefficient of variation of arterial pulsatility index (CVPI) gave complete separation between breathing and apnoeic groups (lower values of VVI and CVPI being associated with the apnoeic group). Hence, when stand alone continuous wave Doppler units are used to acquire umbilical artery Doppler waveforms during fetal apnoea, the presence of apnoea can be determined using the variability of the arterial and venous trace without the need for visualisation of the fetus using imaging equipment.