Quantitation of breathing-related modulation of umbilical arterial and venous flow velocity waveforms in the normal term fetus

Abstract

The effect of fetal breathing activity on umbilical arterial and venous flow velocity waveforms was studied in 11 normal pregnant subjects at term during fetal behavioural state 2F (Nijhuis et al. Early Hum Dev 1982;6:177–195). A total of 1041 breathing cycles was evaluated. Our data suggest a net reduction in venous flow velocity during fetal breathing activity. In contrast to venous flow velocity, the magnitude of breathing-related modulation of arterial pulsatility is small and independent of breathing amplitude. Nevertheless, for clinical purposes umbilical arterial flow velocity waveform recording during fetal apnea is recommended.