Development of Fetal Movement between 26 and 36-Weeks' Gestation in Response to Vibro-Acoustic Stimulation

Abstract

Background: Ultrasound observation of fetal movement has documented general trends in motor development and fetal age when motor response to stimulation is observed. Evaluation of fetal movement quality, in addition to specific motor activity, may improve documentation of motor development and highlight specific motor responses to stimulation.

Aim: The aim of this investigation was to assess fetal movement at 26 and 36-weeks gestation during three conditions (baseline, immediate response to vibro-acoustic stimulation (VAS), and post-response).

Design: A prospective, longitudinal design was utilized.

Subjects: Twelve normally developing fetuses, eight females and four males, were examined with continuous ultrasound imaging.

Outcome measures: The fetal neurobehavioral coding system (FENS) was used to evaluate the quality of motor activity during 10-s epochs over the three conditions.

Results: Seventy-five percent of the fetuses at the 26-week assessment and 100% of the fetuses at the 36-week assessment responded with movement immediately following stimulation. Significant differences in head, fetal breathing, general, limb, and mouthing movements were detected between the 26 and 36-week assessments. Movement differences between conditions were detected in head, fetal breathing, limb, and mouthing movements.

Conclusion: Smoother and more complex movement was observed with fetal maturation. Following VAS stimulation, an immediate increase of large, jerky movements suggests instability in fetal capabilities. Fetal movement quality changes over gestation may reflect sensorimotor synaptogenesis in the central nervous system, while observation of immature movement patterns following VAS stimulation may reflect movement pattern instability.

Keywords: fetal movement; fetal programming; motor development; pregnancy; prenatal.

Figure 1

Each columns represents the average percentage of 10-s epochs for total head movement observed at 26 (columns 1–3) and 36 weeks gestation (columns 4–6). For illustration, a significant increase in total head movement is observed during the immediate response at both the 26 and 36 week assessment between baseline and immediate response (F_(2,22) = 3.71, p = 0.041).

Figure 2

Each column represents the average percentage of 10-s epochs for breathing movements (regular, irregular, and vigorous) and hiccups observed at 26 (columns 1–3) and 36 weeks gestation (columns 4–6). For illustration, regular fetal breathing movements (white) demonstrated an interaction with a decrease in movements during the immediate response period at the 36 week assessment with no difference between baseline and immediate response observed at the 26 week assessment (F_(1,11) = 4.46, p = 0.027).

Figure 3

Each column represents the average percentage of 10-s epochs for all general body movements (smooth and jerky), bacharch, startle, and stretch observed at 26 (columns 1–3) and 36 weeks gestation (columns 4–6). For illustration, jerky general body movements (light grey) are observed less frequently at the 36 week versus 26 week assessment (F_(1,11) = 4.85, p = 0.05).

Figure 4

Each column represents the average percentage of 10-s epochs for total limb movements (large, jerky; large smooth; small jerky; small, smooth) observed at 26 (columns 1–3) and 36 weeks gestation (columns 4–6). For illustration, at both the 26 and 36 week assessment, both large limb jerky (black) and large limb smooth (light gray) increased from baseline to immediate response (F_(1,11) = 8.91, p = 0.012 and F_(1,11) = 6.64, p = 0.026).

Figure 5

Each column represents the average percentage of 10-s epochs for total mouthing movement (non-rhythmic and rhythmic) and yawn observed at 26 (columns 1–3) and 36 weeks gestation (columns 4–6). For illustration, total mouthing movements (columns 1–3 compared to columns 4–6) were observed more frequently at the 36 week assessment (F_(1,11) = 9.77, p = 0.01).