Spontaneous cyclic embryonic movements in humans and guinea pigs.

Motility assessment before birth can be used to evaluate the integrity of the nervous system. Sideways bending (SB) of head and/or rump, the earliest embryonic motility in both humans and guinea pigs, can be visualized sonographically. We know from other species that early embryonic motility is cyclic. This study explores the distribution of SB-to-SB intervals in human and guinea pig embryos before the appearance of more complex movements such as general movements. We hypothesized that the activity in both species is cyclic. We made 15-min sonographic recordings of SBs between 5 weeks and 0 days (5wk0d) and 7wk0d conceptional age (CA) in 18 human embryos of uncomplicated IVF pregnancies (term 38 weeks) and in 20 guinea pig embryos between 3wk4d and 4wk0d CA (term 9 weeks). SB-to-SB interval durations were categorized as long (≥10 s) or short (<10 s) intervals. For human embryos, the median values for long and short intervals were 61 s (range, 10-165 s) and 3 s (range, 1-9 s) respectively; for guinea pigs 38 s (range, 10-288 s) and 5 s (range, 1-9 s), respectively. During development, the duration of long intervals decreased while the number of short intervals increased for both species. The earliest embryonic motility in the human and guinea pig is performed cyclically with distinct developmental milestones. The resemblance of their interval development offers promising possibilities to use the guinea pig as a noninvasive animal model of external influences on motor and neural development.

Fetal onset of general movements.

Perinatal qualitative assessment of general movements (GMs) is a tool to evaluate the integrity of the young nervous system. The aim of this investigation was to study the emergence of GMs. Fetal onset of GMs was studied sonographically in 18 fetuses during the first trimester of uncomplicated in vitro fertilization (IVF) pregnancies in weekly assessments. The earliest motility consisting of small and simple sideways bending (SB) of head and/or rump starts at 7 wk, lasting about 1 s. Between 7 and 8.5 wk, motility differentiates further into movements in which also one or two arms or legs become active; movements are still slow, small, and in one direction, but the duration increases to a few seconds. The transition into GMs at 9-10 wk is characterized by variation in participating body parts and amplitude, speed, and direction during longer periods of time. Between 9 and 13 wk, simple and stereotyped SBs and GMs may coexist. At 9 wk, the incidence of SBs decreases (p = 0.01) and that of GMs increases (p = 0.006). The data suggest that initial simple fetal motility is generated by spinal and brainstem circuitries, and the emergence of complex and variable GMs denotes the onset of supraspinal modulation of this spinal and brainstem activity.