Motor responsivity during habituation testing of normal human fetuses

Abstract

Features of fetal motor responsivity include both the magnitude of the startle response elicited by a single stimulus (i.e., basal reactivity) and the ease by which responding to successive stimuli is inhibited (i.e., habituation). We examined basal motor reactivity and habituation of the motor response in 56 normal human fetuses between 34 and 40 weeks of gestation. Testing consisted of 8 trials of a 1-sec vibroacoustic stimulus (VAS) with a 10-sec interstimulus interval. A score of 0-10 was assigned for each trial based on subjective assessment of intensity and duration of the fetal motor response. Measures of habituation included the ratio of responding after a fixed number of trials divided by the initial response, and the rate of change in the behavioral response over trials. No relationship was found between the rate of motor habituation and either basal reactivity, gestational age, or prestimulus fetal heart rate (FHR) variability. In contrast, more mature fetuses responded less intensely to the first stimulus than did their younger counterparts (r = -0.329, p = 0.005), and fetuses who were initially in a quiet state exhibited a more vigorous startle response as compared to fetuses who were initially in a more active state (r = -0.372, p = 0.001). The relationship between basal reactivity and prestimulus FHR variability was statistically significant even after controlling for gestational age (r = 0.295, p = 0.01). These findings may have important clinical implications regarding the appearance in early life of certain behavioral tendencies such as temperament.

Low Levels of Corticotropin-Releasing Hormone during Early Pregnancy Are Associated with Precocious Maturation of the Human Fetus

“…Thus, there are both in vitro and in vivo findings indicating that the placenta detects and responds to a variety of maternal physiological and psychological stress signals supporting the conclusion that levels of pCRH reflect fetal exposure to maternal stress. This conclusion is supported by findings from several studies that reported an impact of prenatal maternal psychosocial state on human fetal behavior [Van den Bergh et al, 1989; Groome et al, 1995; Sjostrom et al, 1997; Monk et al, 2000; DiPietro et al, 2002; Monk et al, 2003]. …”

Maternal depression and anxiety effects on the human fetus: Preliminary findings and clinical implications

“…Fetal reaction usually entails a startle response consisting of increased movement and heart rate that then declines over trials (Groome, Singh, Burgard, Neely, & Deason, 1995;Groome, Watson, & Dykman, 1994). Fetal response to vibratory stimulation begins at about the 26th week of gestation and reaches maturity at about 32 weeks (Kisilevsky, Muir, & Low, 1992).…”

Fetal Habituation

“…63 In contrast to studies which have presented stimuli until the fetus ceases responding, 31 ' 34 others have not habituated the fetus until the cessation of the response but have presented a fixed number of stimuli (e.g. 3, M 8, 37 14, 35 20, 43 40, 47 ) and noted the fetus's response to this. This is an inherent problem in the latter type of study in that individuals may not be equally habituated when the final stimulus of the sequence has been presented.…”