AN ESTIMATE OF FETAL AUTONOMIC STATE BY SPECTRAL-ANALYSIS OF HUMAN UMBILICAL ARTERY FLOW VELOCITY WAVE-FORMS

Objective: Determination of gestational age-related fluctuations in he art rate in the umbilical artery of the early human fetus, Methods: Do ppler velocity recordings from human umbilical artery were obtained, i n a cross-sectional study design in 137 singleton pregnancies at 10-20 weeks of gestation. After exclusion criteria were applied, data on 11 7 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 ra te variability decreases at 10-20 weeks and demonstrates a shift to lo wer frequencies at 17-20 weeks. Conclusions: Fetal heart rate variabil ity is related to gestational age and shows a shift to lower frequenci es which may reflect autonomic functional development. (C) 1998 Elsevi er Science B.V.