The evolution of primitive reflexes in extremely premature infants.

A longitudinal study describes the pattern of appearance of eight primitive reflexes in a population of 47 viable extremely premature infants, beginning as early as 25 wk postconceptional age (PCA). Infants were examined weekly, from 1 wk of age until discharge from the neonatal intensive care unit. Primitive reflexes were graded as to completeness and intensity of response. Three patterns emerged: the upper and lower extremity grasp reflexes were present in all premature infants, from 25 wk and beyond, the Moro, asymmetric tonic neck reflex and Galant (lateral trunk incurvature reflex) were present in some premature infants as early as 25 wk PCA, and in the majority by 30 wk PCA, and the lower extremity placing, positive support, and stepping were occasionally present prior to 30 wk PCA, yet were not uniformly present and/or complete even at term. In each case, the primitive reflex became stronger, more complete, more consistently elicited and more prevalent with increasing postconceptional age. The pattern of primitive reflexes in the premature infant at term (40 wk PCA) is similar to that of full-term newborns. Sequential assessment of the primitive reflexes may be a useful method of evaluating extremely premature infants prior to term.