Electromyographic evaluation of the moro reflex in preterm, term, and small-for-dates newborn infants

AbstractThe Moro reflex motor response was studied by electromyographic analysis of extensor and flexor activity in normal fullterm, preterm, and small-for-dates fullterm infants. Flexor motoneuron activity increased significantly with maturation, whereas duration and amount of extensor motoneuron activity remained constant. The triceps/biceps Moro response activity quotient decreased with conceptional age. Rhythmic Moro response activity occurred in normal fullterm, small-for-dates, and preterm newborn infants above 34 weeks conceptional age. A special type of Moro response with delayed flexor activity was found more often in preterm than in fullterm newborn infants. The Moro response was not found suitable for an exact estimation of conceptional age. Particularly in small-for-dates infants, the Moro response pattern was influenced more by pathophysiological factors than by age differences.