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Fetal DiagnTher 1993;8:209-210
E.Z. Zimmer
P. Jakobi
R. Talmon
R. Shenhav
A. Weissman
White Noise Does Not Induce
Fetal Sleep
Departments of Obstetrics and
Gynecology, and Otolaryngology,
Rambam Medical Center,
Technion, Faculty of Medicine,
Haifa, Israel
Abstract
White noise has been shown to induce sleep in newborns. We
sought to examine whether this type of sound will also induce
a quiet state in the fetus. Twenty-two fetuses at 36-41 weeks of
gestation were exposed to white noise during an active state.
The sound was delivered for 5 min at an intensity of 100 dB.
No significant change in fetal activity was noted following the
sound.
Introduction
In the prenatal period, a quiet fetus is ben­
eficial when invasive intrauterine procedures
are performed. Fetal movements may dis­
place the needle during umbilical blood sam­
pling or transfusions and cause fetal hemor­
rhage [1], Waiting for a spontaneous quiet
behavioral state to occur in the fetus is some­
times time-consuming, therefore some inves­
tigators have used medication of mothers and
even curarization of fetuses in order to reduce
fetal activity during these procedures [1,2]. In
active and even crying newborns, sleep can be
induced by exposure to white noise [3,4], We
Received:
July 24.1992
Accepted:
September 2. 1992
sought to examine whether white noise can be
used as a noninvasive method to induce a
quiet sleep-like state in the fetus.
Materials and Methods
Twenty-two healthy women at 36-41 weeks of ges­
tation were enrolled in the study after giving an
informed consent. All fetuses were normal and in ver­
tex presentation. Fetal heart rate (FHR) was recorded
with an external monitor. Fetal movements were re­
corded by the mothers who had headphones to obscure
external sounds. The fetal state was classified as active
or quiet [5]. Periods of increased FHR variability,
FHR accelerations and fetal movements were consid­
ered as an active state. Periods of decreased FHR vari-
E.Z. Zimmer, MD
Department of Obstetrics and Gynecology
Columbia Presbyterian Medical Center
622 West 168th Street
New York. NY 10032 (USA)
© 1993
S. Kargcr AG. Basel
1015-3837/93/
0083-020952.75/0
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KeyWords
White noise
Sleep
ability and absence of fetal movements and FHR
accelerations were considered as a quiet state.
All studies were performed during periods of fetal
activity. The sound device was located above the ma­
ternal abdomen over the fetal head. A white noise was
delivered for 5 min at an intensity of 100 dB measured
at the surface of the maternal abdomen.
Results
Baseline FHR, variability and number of
accelerations during the period of sound stim­
ulation were compared to two control epochs
of 5 min both before and after the sound stim­
uli presentation periods. No significant differ­
ence was observed in any of these parameters
between the control and study periods.
Discussion
Fetal responses to sound stimuli have been
studied for many years. Most investigators
have focused on the fetal startle response to
high intensity stimuli as a measure of fetal
well being. Recently, Lecanuet et al. [6] found
that sound stimuli of lower intensities (95100 dB) evoked FHR decelerations. From a
psychobiological perspective, it has been sug­
gested that heart rate accelerations arc a com­
ponent of a defensive response, while heart
rate decelerations are indicative an of orient­
ing or attentional response [7, 8],
In our study, we therefore presented a
stimulus at an intensity of lOOdB. We as­
sumed that if fetuses orient to the white noise,
a change in state from active to quiet will be
noted, similar to the finding in neonates.
However, such a change in behavior was not
observed in the fetuses. At present we can
only speculate as to a possible reason for these
negative findings. As shown by Querleu et al.
[9] sound stimuli ex utero are characterized
by a complex structure of harmonics which
are attenuated when transduced in utero. This
suggests that the sound experienced in utero is
diminished in its structural complexity due to
attenuation. Therefore, the results we ob­
served may be due to the fact that the fetuses
did not experience the full harmonic com­
plexity of the harmonic components of white
noise.
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Berg KW: Cardiac orienting re­
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White Noise Stimulation of the Fetus
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