Effect of gestational age on neurological functioning of the very low-birthweight infant at 40 weeks

A cohort of 97 very low-birthweight infants who had had prolonged care in two neonatal units was identified prospectively and subdivided into three groups according to gestational age at birth (23 to 27, 28 to 31 and 32 to 36 weeks). The neurological status of the three groups was compared at 40 weeks gestational age. The effects of various medical complications also were analyzed by comparing the neurological performances at term of nine 'at-risk' fullterm infants with 'complicated' preterm infants, and 15 'normal' fullterm infants with 'healthy' preterm infants. After controlling for medical complications, no significant difference in neurological scores was found between the three preterm groups, nor between the preterm groups and the 'at-risk' fullterm group. However, 'healthy' preterm infants had significantly lower scores than fullterm 'normal' infants. Item analyses also showed significant differences between the three preterm groups: those with gestations between 23 and 27 weeks were more likely to exhibit tremors than the other two groups; and those with gestations of 32 to 36 weeks were more likely to have opisthotonic postures, overshooting movements, hypertonus and exaggerated responses. While preterm infants in general do not differ in neurological functioning from 'at-risk' fullterm infants, they do differ significantly from 'normal' fullterm babies. Similarly, some groups of infants born too soon exhibit specific neurological features which differentiate them from their preterm counterparts.