Normal values for the soleus H-reflex in newborn infants 31-45 weeks post conceptional age

Normal values for the soleus H-reflex were established in 83 preterm and term infants 31 to 45 weeks postconceptional age. Infants at conceptional ages 31 to 34 weeks (n = 30) had a mean H-latency (msec) of 19.2 +/- 2.16; infants 35 to 39 weeks (n = 26), 16.67 +/- 1.48; and infants 40 to 45 weeks (n = 27), 15.94 +/- 1.45. Simple linear regression shows a significant relationship between conceptional age and H-latency (Pearson correlation = .68, R2 = 0.47, f = 71.31, p = .0001). Adjusting H-latency values for leg length, the regression of H-soleus latency/leg length (msec/cm) against conceptional age provides an even stronger relationship (r = 0.81, R2 = 0.66, f = 154.5, p = .0001). These results reflect the degree of myelination in infants of increasing conceptional ages. They can indicate the gestational age of the infants and afford comparative data in the event of peripheral nerve pathology.