Prediction of gross motor development and independent walking in infants born very preterm using the Test of Infant Motor Performance and the Alberta Infant Motor Scale
Introduction
Advantages in neonatal intensive care have improved the survival rate of infants born at younger gestational ages [1]. The incidence of infants with very premature birth (< 32 weeks gestation) who survived the neonatal period was 9.6/1000 in 2008, and of infants < 30 weeks 3.3/1000 according to the Netherlands Perinatal Registration (www.perinatreg.nl). The younger the gestational age (GA) or the lower the birth weight (BW), the more risk factors for delayed or impaired development [2], [3], [4]. Infants with a GA < 30 weeks are at high risk, therefore their neuromotor development is often monitored in a neonatal follow-up clinic. One of the objectives of a neonatal follow-up program is to predict gross motor outcome and target those infants who might benefit from early intervention. For parents it is important to know if and when their child might start to walk independently [5], [6].
Motor skill acquisition is influenced by infant, cultural and contextual factors [7], [8]. Compared to their full-term born counterparts, infants born preterm are delayed in the onset of walking [9], [10], [11], [12]. Infant factors, like neuromaturation, postural control, and muscle strength play an important role in the development of walking skills [13], [14], [15]. The Alberta Infant Motor Scale (AIMS) measures early gross motor development [16] and the Test of Infant Motor Performance (TIMP) postural and selective motor control needed for functional performance in early infancy [17]. The concurrent validity of these instruments, both designed to apply early in life, and their ability to identify infants with a suspect motor development has been described as fair to good [18], [19], [20]. Considering the different constructs of both tests, the question arose, which instrument would be of better clinical value predicting gross motor development in the neonatal follow-up. In the present study we analyzed the predictability of gross motor development and independent walking in a birth cohort of infants born very preterm, comparing the two tests.
The objectives were:
- 1.
To assess the concurrent validity and diagnostic agreement between the TIMP and the AIMS used at three months corrected age (CA) in infants born at < 30 weeks of gestation or with a BW < 1000 g.
- 2.
To determine the ability of the TIMP and the AIMS to predict the level of gross motor maturation and independent walking around 15 months CA.
- 3.
To explore predictors associated with the age of independent walking.
Section snippets
Design and subjects
The participants in this study were recruited as part of a longitudinal study on motor performance of infants born very preterm in or referred to a level three neonatal intensive care unit within one week of birth, from January 2009 through to October 2010. Inclusion criteria were: infants born at a GA < 30 weeks or with a BW < 1000 g, who participated in the neonatal follow-up program. Infants diagnosed with chromosomal, genetic, major neurological or sensory abnormalities were excluded. The
Results
During the study period, 158 infants born with a GA < 30 weeks or a BW < 1000 g started the neonatal follow-up program around term-equivalent age. Due to social reasons or long traveling distance to the hospital, the parents of 10 infants were not approached. Ten more parents declined to participate. From the remaining 138 infants, 17 (12%) had to be excluded due to medical conditions: two infants presented with a sensory system disorder (one auditory, one visual), seven with a congenital
Discussion
Fifty percent of the examined infants born very preterm walked independently at 15.7 months CA. Compared to the AIMS norm values of predominantly term born infants, the median onset was more than three months later [16], even though their age was corrected for prematurity. This result is based on a selection of relatively healthy infants, because infants with known medical conditions that were considered to delay their gross motor development were excluded. In non-Western infants, independent
Conclusions
Despite good concurrent validity, neither the TIMP nor the AIMS administered at 3 months CA can reliably predict gross motor maturation or walking skills at 15 months CA in infants born very preterm. A clinical implication is that the age of three months might be too early to assess infants if the goal is to give any valid prediction on later gross motor outcome. This indicates also that no valid prediction of gross motor development and the age of independent walking could be given prior to six
Conflict of interest
The authors declare they have no conflict of interest.
Acknowledgments
We gratefully acknowledge Dr. Marian Jongmans for support in the examinations of the 15-months old infants, Cas Kruitwagen MSc for his advice on the statistical analyses of the study, and most importantly, all the families who participated in this study.
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