Muscle power in 'high-risk' preterm infants at 12 and 24 weeks corrected age:a measure for early detection

A group of 72 "high-risk" preterm infants was studied at the corrected ages of 12 and 24 wk. Onlyinfants with a high risk for developmental deviance with gestational ages below 32 wk and/or birthweights of less than 1500 g were included in the study. In addition, the infants were categorized according to their medical history, as confirmed by the "Neonatal Medical Index" (NMI I to V), with category I describing infants with few medical problems and V characterizing those with the most serious complications. In this study we included only "high-risk" infants as categorized in NMI III to V, since infants with a "low risk" have been described earlier. Apart from the standard paediatric follow-up, an age-adequate neurological assessment was made, with special emphasis on the relationship between active and passive muscle power. When development is optimal, these two components of muscle power should be in balance in order to create a stable posture and fluent motility. We compared muscle power at the corrected ages of 12 and 24 wk to determine whether the method employed to assess muscle power could enhance early detection of deviant development. At 12 wk of age, only 5 infants showed overall optimal muscle power, while at 24 wk this figure had increased to 27. Significantly more infants in NMI III had optimal outcomes at 24 wk of age. When muscle power in the different parts of the body was studied separately at 24 wk, outcomes in shoulders and trunk still showed significant discrepancies in all NMI groups. At this age, fewer asymmetries were found compared to outcomes at 12 wk. Conclusion: Our method of assessing muscle power is useful in detecting preterm infants at risk for pathological development.