Neuromotor development in relation to birth weight in rabbits.

The development of neuromotor patterns in relation to birth weight was studied in the rabbit, a perinatal brain developer. In order to induce intrauterine growth retardation and to increase the number of low birth weight rabbits, experimental ischemia to half the fetuses in each doe was achieved by total ligation of approximately 30% of spiral vessels to the placenta, during the last trimester of gestation. Following natural delivery, the rabbit pups were periodically observed for the appearance of eye-opening and righting reflex, and for the cessations of falling, circling and dragging of hind limbs. An index of neuromotor development was assigned to each rabbit by summing up the age (in days) of appearance of each of the neuromotor milestones. An association was found between low birth weight and delayed neuromotor development at 2 weeks of age. The most significant correlation was found between low birth weight and delayed disappearance of falling. The latter may represent incoordination as an expression of cerebellar dysfunction.