Sleep-wake cycles in normal fetuses.
OBJECTIVE
To study the normal ranges of sleep-wake cycles in normal fetuses.


METHODS
A total of 600 fetal heart rate (FHR) tracings were studied from uncomplicated singleton pregnancies at a gestational age between 30 and 40 weeks with a 1-h recording. Two obstetricians interpreted all the FHR recordings independently.


RESULTS
The mean baseline FHR was 141.6 (7.6) beats/min. The median relative percentage time spent in a quiet state was 26% (0-88.6). The median duration of time spent in a quiet state was 15.7 min (0-53.2) within a 1-h recording. Both quiet and active states were established in 84% of cases. The number of FHR accelerations per hour in an active state increased with advancing gestational age, whereas the baseline FHR gradually decreased.


CONCLUSIONS
Normal ranges of fetal sleep-wake cycles were established. Fetuses between 30 and 40 weeks had wide variations in the percentage of time spent in sleep-wake states.
Suwanrath
Chitkasaem
C
Department of Obstetrics and Gynecology, Prince of Songkla University, Hat Yai, Songkhla 90110, Thailand. schitkas@yahoo.co.uk
Suntharasaj
Thitima
T
D000328:Adult; D015148:Cardiotocography; D005260:Female; D005333:Fetus / Q000502:physiology*; D005865:Gestational Age; D006340:Heart Rate, Fetal; D006801:Humans; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D012016:Reference Values; D012890:Sleep / Q000502:physiology*; D055815:Young Adult