Background: Although a number of measures exist that can be used to follow maturation of central nervous system (CNS) structure (e.g. ultrasound, MRI) and postnatal CNS function (e.g. developmental milestones), there are currently no measures that follow maturation of CNS function prior to term.

Method: Based on previous assessments of the evolution of tone and reflexes prior to term in extremely preterm infants1,2, we developed a numerical maturity score, a sum of degree of flexor tone and posture, axial tone, DTRs, pathological reflexes (e.g. Babinski), primitive reflexes (e.g. Moro), oromotor function and sensory responses. This maturity score was calculated from weekly neuro-developmental examinations3 in all low risk VLBW infants (<1500 gms) born in a two year period from June, 1994 to July, 1996(n=54) who did not have intracerebral hemorrhage or echodensities, oxygen ≥ 28 days, in utero exposure to illicit drugs, SGA or perinatal depression. For each infant, maturity scores were plotted against postmenstrual age (PMA). A line of best fit was then drawn using SPSS, with calculation of R2, slope and y intercept at 32 weeks PMA.

Results: Mean BW was 1067 gms (range 620-1465); gestational age was 28 weeks (24 - 32). There were 16 (30%) multiples, 30 (55%) males and 33(61%) African Americans. There were a total of 368 exams in 54 infants, a mean of 8 (3-16) per infant. In all cases of this standard sample, the maturity score increased linearly with PMA, with a mean R2 of 0.91 (0.63-1.00) with the line of best fit. The mean slope was 6.87 (2.75-10.71) and the mean y intercept at 32 weeks PMA was 53.67 (40-73).

Conclusion: The maturity score appears to measure maturation of tone and reflexes prior to term in this standard sample of low risk extremely preterm infants. Further research will evaluate its relationship to factors related to outcome, later disability and new neonatal treatments for CNS injury in VLBW infants.