Muscle power and medical history in high risk preterm infants at 3 months of corrected age.

A group of 73 "high risk" preterm infants was studied at the corrected age of 12 weeks. The infants were categorized according to their medical history in 5 classes conform with the "Neonatal Medical Index" (NMI). Only infants with high-risk for developmental discrepancies with a score of NMI > or = III were included in the study. Apart from pediatric follow-up and an age-adequate neurological examination, special emphasis was put on measuring a specific feature in the development of preterm infants: the relationship between active muscle power and passive tone. These two components of muscle power should be in balance with each other to create stable posture and fluent motility and later co-ordination. Discrepancy between active and passive muscle tone was found in all NMI groups studied and was most outspoken in the legs. Infants in NMI IV and V showed a significantly higher incidence of increased passive tone than the infants in NMI III. When the different regions of the body were studied separately, the infants in NMI IV and V showed significantly increased passive tone in the trunk and shoulders (p 0.009) compared to infants in NMI III, which may constitute an alarm signal of deviant development. The main aim of the study was to provide a clinical method for early detection, subtle enough to select infants most at risk for later functional and neurological problems.