Periodic spectral components of fetal heart rate variability reflect the changes in cord arterial base deficit values: a preliminary report

Fetal distress changes the function of the autonomic nervous system. These changes are reflected in the fetal heart rate and can be quantified with po wer spectrum analysis of heart rate variability. The purpose of this study was to find out whether spectral components of fetal heart rate variability (FHRV) during labor are associated with fetal cord arterial base deficit v alues at birth. The association between FHRV and umbilical cord arterial ba se deficit was studied in 14 singleton fetuses with normal pregnancy at 35- 40 weeks of gestation. Fetal ECG was recorded by scalp-electrode using a ST AN(R) Fetal ECG monitor (Cinventa Ab, Molndal, Sweden). FHRV was quantified by computing Fast-Fourier-transformed heart rate (HR) spectra at three fre quency bands: low-frequency (LF) 0.03-0.07 Hz, mid-frequency (MF) 0.07-0.13 Hz and high-frequency (HF) 0.13-1.0 Hz. We found that total FHRV and MF FH RV were lower in fetuses with cord arterial base deficit 8 to 12 mmol/L in comparison to the fetuses with normal cord arterial base deficit value (P = 0.02 and P = 0.01, respectively). A linear con-elation was found between t he spectral densities and the cord arterial base deficit values (r = 0.4 an d r = 0.6, respectively). We conclude that the results suggest changes in t he autonomic nervous cardiac control in fetuses with cord arterial base def icit between 8 to 12 mmol/L. The clinical applicability of our observations on FHRV in predicting fetal distress remains to be further studied. (C) 20 01 Elsevier Science Ireland Ltd. All rights reserved.