Journal of Ultrasound in Medicine, Vol 8, Issue 4 215-218, Copyright © 1989 by American Institute of Ultrasound in Medicine
Effect of fetal heart rate on umbilical arterial Doppler indices
P. Yarlagadda, L. Willoughby and D. Maulik
School of Medicine, University of Missouri, Kansas City.
Umbilical arterial Doppler indices (UaDI) are recognized as potentially
useful tools for fetal surveillance. However, elucidation of the diagnostic
reliability of UaDI requires further analysis of the factors that affect
the variance of the indices. This prospective study was undertaken to
analyze the effects of one such factor, the fetal heart rate (FHR). The
study population consisted of 194 cases of uncomplicated pregnancy with
normal outcome, with the gestational age (GA) ranging from 27 to 39 weeks.
A continuous wave Doppler instrument with a 4-MHz transducer was used. The
UaDI measured were diastolic/average (D/A) ratio, systolic/diastolic (S/D)
ratio, pulsatility index (PI), and resistance index (RI). Linear regression
of the data grouped in 2 week GA intervals demonstrated a moderate but
statistically significant (p less than .05) correlation between FHR and
UaDI. The influence of FHR on UaDI was then further analyzed by multiple
regression technique using GA as the second independent variable. The
regression demonstrated that 15% to 18% of the total UaDI variance was
attributable to FHR effect. Moreover, when UaDI data were standardized for
a FHR of 140 beats per minute and GA of 34 weeks using a multiple
regression-based equation, the 95% limits of the UaDI were reduced by 32%,
34%, 26%, and 32% for D/A, S/D, PI, and RI, respectively. This study
demonstrates a statistically significant effect of FHR on UaDI. However,
clinical significance of this observation requires further investigation.
