Quantitative analysis of fetal general movements: methodological considerations.
OBJECTIVE
We studied the effects of gestational age and various smoothing procedures on four incidence parameters of fetal general movement, to evaluate reported variation in previous studies and to establish the optimal way of smoothing.


METHODS
General movements were studied longitudinally between 24 and 40 weeks of gestation in 29 healthy fetuses. The number of movement bursts per hour, burst duration, onset-onset interval between successive bursts (OOI) and the percentage incidence were analysed in detail.


RESULTS
Advancing gestation was characterised by a proportional increase in OOI's lasting > 60 s and a decreased number of bursts, whereas burst duration remained relatively stable (unsmoothed data). Smoothing resulted in an exaggerated decrease in the number of bursts and in increases in burst duration, OOI and percentage incidence. These changes occurred in a gestational age specific manner and could largely explain the variation in results between previous studies.


CONCLUSIONS
The temporal patterning of fetal general movements undergoes developmental change, as shown by differential effects of smoothing between mid and late pregnancy. A smoothing procedure is to be preferred which includes short intervals (1-3 s) between the elements composing a burst, since small changes in movement generation can still be recognised this way.
ten Hof
J
J
Department of Obstetrics, University Hospital of Utrecht, The Netherlands.
Nijhuis
I J
IJ
Nijhuis
J G
JG
Narayan
H
H
Taylor
D J
DJ
Visser
G H
GH
Mulder
E J
EJ
D000328:Adult; D001724:Birth Weight; D003627:Data Interpretation, Statistical; D005260:Female; D005324:Fetal Movement / Q000502:physiology*; D005333:Fetus / Q000502:physiology*; D005865:Gestational Age; D006801:Humans; D008432:Mathematical Computing; D011247:Pregnancy; D015203:Reproducibility of Results; D016216:Ultrasonography, Prenatal