Developmental Trends in Fetal Habituation to Vibroacoustic Stimulation

Abstract

Habituation is a measure of the ability to inhibit responding and is a more mature form of behavior than is persistent responding. We examined the developmental trend in habituation of the fetal startle response to repeated vibroacoustic stimulation in 90 normal human fetuses between 28 and 40 weeks of gestation. Fetal movement was graded according to the nature of the behavioral response: general startle (3), fast limb movement (2), slow rolling movement (1), and no movement (0). A significant developmental difference (p < 0.0004) in the rate of habituation was found, with response decrement occurring faster in fetuses of more than 32 weeks of gestation. Furthermore, by dividing the patients into three gestational age groups, it was determined that the greatest change in the rate of habituation occurred between 28 and 32 weeks and 32 and 36 weeks. We conclude that the rate of fetal habituation may be determined by the degree of maturation of the neural circuitry governing this form of nonassociative learning.

Neurobehavioral assessment before birth

“…Although development (increase or decrease) in each domain continues through term, the 32-week fetus is more similar to a term fetus than to a fetus prior to this transitional period. These findings based on statistical modeling techniques, confirm numerous reports by others, including those for heart rate patterns [Gagnon et al, 1987], fetal breathing [Pillai and James 1990c;Kozuma et al, 1991], total motor activity and specific motor patterns [Roberts et al, 1980;Patrick et al, 1982b;Roodenburg et al, 1991], duration of quiescence and other state indicators [Visser et al, 1987;James et al, 1995;, responsiveness to vibroacoustic stimuli [Kuhlman et al, 1988;Kisilevsky et al, 1992], and habituation [Groome et al, 1993]. This time period corresponds to assumption of higher order control within the developing fetal brain [Yoshizato et al, 1994].…”

“…In the 1920s and 30s, stimuli included an electronic door buzzer [Sontag and Wallace, 1935] and a warning horn [Peiper, 1925 as cited in Sontag andWallace, 1935]. More recent stimuli include an electric toothbrush [Leader et al, 1984], an artificial electronic larynx [Gagnon et al, 1989], and a device designed for clinical fetal stimulation [Groome et al, 1993;DiPietro et al, 1996b]. The term vibroacoustic refers to stimuli activated on or at the level of the maternal abdomen, usually above the fetal head.…”

“…Fetal habituation to auditory and/or vibratory stimuli has been documented [Leader et al, 1984;Madison et al, 1986;Kuhlman et al, 1988;Goldkrand and Litvack, 1991;Groome et al, 1993;Sandman et al, 1997;van Heteren et al, 2000]. However, with few exceptions [Hepper and Shahidullah, 1992;Sandman et al, 1997], dishabituation is not assessed, making it difficult to distinguish true habituation from response fatigue.…”

“…Statistical efforts to reduce some of the interpretative issues raised in an earlier section regarding the definition of habituation responses are in progress [Ratcliffe et al, 2002], but these do not address the eth-ical issues raised by repetitively stimulating the fetus. Presentations of 15 to 50 trials have been reported [Leader et al, 1984;Groome et al, 1993;Sandman et al, 1997;Gingras and O'Donnell, 1998;van Heteren et al, 2000]. There is debate over the safety of single applications even within the context of clinical fetal assessment to inform obstetric management [Zimmer and Divon, 1993]; repeated applications clearly compound these concerns.…”

Fetal Habituation

“…Studies of fetal motor responses to repeated stimulation have shown that this response changes with gestation. 35 At later gestations the magnitude of the motor response decreases more rapidly with repeated stimulus presentations. However it is unclear whether this reflects the development of the habituation response per se or (more likely) reflects changes in fetal motor development.…”