Power spectrum analysis of fetal heart rate variability at near term and post term gestation during active sleep and quiet sleep.
BACKGROUND
Spectral analysis of fetal heart rate variability is promising for assessing fetal condition. Before using spectral analysis for fetal monitoring it has to be determined whether there should be a correction for gestational age or behavioural state.


OBJECTIVE
Compare spectral values of heart rate variability between near term and post term fetuses during active and quiet sleep.


METHODS
Case-control. Cases had a gestational age of > or =42 weeks; controls were 36 to 37 weeks. Fetuses were matched for birth weight percentile.


METHODS
STAN registrations from healthy fetuses. For each fetus one 5-minute segment was selected during active and one during quiet sleep.


METHODS
Absolute and normalized low (0.04-0.15 Hz) and high frequency power (0.4-1.5 Hz) of heart rate variability.


RESULTS
Twenty fetuses were included. No significant differences were found between cases and controls in absolute (481 and 429 respectively, P=0.88) or normalized low (0.78 and 0.80 respectively, P=0.50) or absolute (41 and 21 respectively, P=0.23) or normalized high frequency power (0.08 and 0.07 respectively, P=0.20) during active state. During rest, normalized low frequency power was lower (0.58 and 0.69 respectively, P=0.03) and absolute (16 and 10 respectively, P=0.04) and normalized high frequency power were higher (0.21 and 0.14 respectively, P=0.01) in cases compared to controls. Absolute and normalized low frequency power were higher during active state compared to rest in both groups (all P values <0.05).


CONCLUSIONS
We found sympathetic predominance during active state in fetuses around term. Post term parasympathetic modulation during rest was increased compared to near term.
van Laar
J O E H
JO
Department of Obstetrics and Gynecology, Máxima Medical Centre, De Run 4600, 5504 DB, Veldhoven, The Netherlands. joehvanlaar@hotmail.com
Peters
C H L
CH
Vullings
R
R
Houterman
S
S
Oei
S G
SG
D016022:Case-Control Studies; D004562:Electrocardiography / Q000379:methods; D005260:Female; D005323:Fetal Monitoring / Q000379:methods; D005324:Fetal Movement / Q000502:physiology; D006340:Heart Rate, Fetal / Q000502:physiology*; D006801:Humans; D007231:Infant, Newborn; D007233:Infant, Postmature / Q000502:physiology*; D008297:Male; D011247:Pregnancy; D012815:Signal Processing, Computer-Assisted; D012890:Sleep / Q000502:physiology*; D013057:Spectrum Analysis / Q000379:methods*; D047929:Term Birth / Q000502:physiology*; D016216:Ultrasonography, Prenatal / Q000379:methods