Behavioral states and breathing activity in the fetus near term.

Measurement of fetal breathing movements (FBM) has found considerable clinical interest recently, because it is thought to be predictive of fetal health or compromise. However, from our investigations on fetal state behavior [7, 8] methods for assessing FBM generally used so far seem to be inadequate and results are suspect of being unreliable: in the fetal lamb and in the rhesus monkey fetus FBM were found to be associated only with active sleep [3,6, 15], and in our investigations in the human fetus we found a duration of quiet sleep periods of 20.4 ± 7.0 min (Mean ± SD) and a duration of active sleep periods of 56.6 ± 20.3 min [7]. Thus results of FBM measurements might be influenced substantially by the ratio of quiet and active sleep within short FBM observation periods of 30 min duration, used by the majority of investigators. This influence on. FBM measurements would be independent of the fetal health state. For a better insight into this problem we performed and evaluated a series of simultaneous recordings of FHR and fetal motor activity (both for assessment of state behavior) and FBM in uncomplicated pregnancies near term.