An estimate of fetal autonomic state by spectral analysis of human umbilical artery flow velocity waveforms.

OBJECTIVE

Determination of gestational age-related fluctuations in heart rate in the umbilical artery of the early human fetus.

METHODS

Doppler velocity recordings from human umbilical artery were obtained, in a cross-sectional study design in 137 singleton pregnancies at 10-20 weeks of gestation. After exclusion criteria were applied, data on 117 normal pregnancies were available and subdivided into group I: 10-12 weeks (n = 49); group II: 13-16 weeks (n = 43); and group III: 17-20 weeks (n = 25). Blood flow velocity waveforms were reconstructed from Doppler audio signals. Variability in heart rate was calculated using Fast Fourier Transforms (FFT). Individual heart rate variability power spectra were subdivided into frequency bands.

RESULTS

Fetal heart rate variability decreases at 10-20 weeks and demonstrates a shift to lower frequencies at 17-20 weeks.

CONCLUSIONS

Fetal heart rate variability is related to gestational age and shows a shift to lower frequencies which may reflect autonomic functional development.