Muscle power development during the first year of life predicts neuromotor behaviour at 7 years in preterm born high-risk infants.

The aim of the study was to find if neurological function during the first year of life could predict neuromotor behaviour at 7 years of age in children born preterm with a high risk. A follow-up study of neuromotor behaviour in 52 children at a mean age of 3, 6, 12 months (corrected age) and 7 years was performed. All children were born with a gestational age less than 32 weeks and/or a birthweight under 1500 g and the infants were categorised according to their medical history in the three highest categories of the 'Neonatal Medical Index' (NMI, from category I to V, from few to serious complications). In addition, neonatal cerebral ultrasound abnormalities were used to divide the infants further into the different NMI categories. At 3 and 6 months, the relationship between active and passive muscle power was measured in shoulders, trunk and legs and (a)symmetry between right and left was noted. The results at 3 and 6 months were ranged from 1 for optimal to 5 for poor muscle power regulation. At 12 months of age, a neurological examination was done with special emphasis on the assessment of postural control, spontaneous motility, hand function and elicited infantile reactions with special attention to (a)symmetry. Outcome at 12 months was expressed as percentage of the optimal score on each subcategory. At 7 years, the motor behaviour study based on Touwen's examination for minor neurological dysfunction was performed. This investigation focuses on different functions, such as hand function, quality of walking, posture, passive muscle tone, coordination and diadochokinesis. The outcome was expressed as percentage of the optimal score on the combined subcategories. The best prediction of neuromotor behaviour at 7 years was assessed with stepwise linear multiple regression, using as potential predictors perinatal factors and outcome of motor behaviour at the corrected age of 3, 6 and 12 months. At 7 years none of the children scored 100% on the combined subcategories, 15 children (29%) scored between 75% and 99%, whereas 15 children scored less than 50%. Neuromotor behaviour at 7 years could be predicted by the NMI categorisation and gender with a sensitivity of 92% (specificity 47%; positive and negative predictive value 81% and 70%). No direct relation was found between neuromotor behaviour and cerebral ultrasound classification only, days on the ventilator and/or continuous positive airway pressure, birthweight, gestational age and dysmaturity. The best predictor of neuromotor behaviour at 7 years was the combination of outcome of muscle power in shoulders and legs at 3 months and postural control at 12 months, taking into account the gender of the child (sensitivity 95%; specificity 40%; positive predictive value 80%; negative predictive value 75%).