Elsevier

Early Human Development

Volume 89, Issue 9, September 2013, Pages 693-697
Early Human Development

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

https://doi.org/10.1016/j.earlhumdev.2013.04.016Get rights and content

Abstract

Background

One objective of a neonatal follow-up program is to examine and predict gross motor outcome of infants born preterm.

Aims

To assess the concurrent validity of the Test of Infant Motor Performance (TIMP) and the Alberta Infant Motor Scale (AIMS), the ability to predict gross motor outcome around 15 months corrected age (CA), and to explore factors associated with the age of independent walking.

Methods

95 infants, born at a gestational age < 30 weeks, were assessed around 3, 6 and 15 months CA. At 3 months CA, correlations of raw-scores, Z-scores, and diagnostic agreement between TIMP and AIMS were determined. AIMS-score at 15 months CA and parental-reported walking age were outcome measures for regression analyses.

Results

The correlation between TIMP and AIMS raw-scores was 0.82, and between Z-scores 0.71. A cut-off Z-score of − 1.0 on the TIMP had 92% diagnostic agreement (κ = 0.67) with an AIMS-score < P10. Neither TIMP- nor AIMS-scores at 3 months CA were associated with the gross motor outcome at 15 months CA. The AIMS-scores at 6 months CA predicted the AIMS-scores at 15 months CA with an explained variance of 19%. Median walking age was 15.7 months CA, with which only the hazard ratio of the AIMS at 6 months CA and ethnicity were significantly associated.

Conclusions

Prediction of gross motor development at 15 months CA and independent walking was not possible prior to 6 months CA using the AIMS, with restricted predictive value. Cultural and infant factors seem to influence the onset of independent walking.

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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