Bartlett, Doreen J. PT, PhD; Nijhuis-van der Sanden, Maria W. G. PPT, PhD; Fallang, Bjørg PT, PhD; Fanning, Jamie Kneale PT, MClSc; Doralp, Samantha PhD
INTRODUCTION AND PURPOSE
Despite improvements in standard of living (ie, social determinants of health), preconceptual and prenatal health care, and technology over the past 2 decades, the incidence of preterm birth has increased, accounting for 6% to 15% of all deliveries.1 Indeed, technology has contributed to both greater survival and the experience of greater morbidity of the most vulnerable of these infants.2,3 Consequences of preterm birth include cerebral palsy (CP) and learning disabilities,1 diagnoses that are associated with long-term rehabilitation needs. Infants born preterm who are at greatest risk for adverse developmental outcomes are those born before 32 weeks of completed gestation4 and are the subgroup of interest in our work. Evidence also suggests that children born preterm who are not diagnosed with a neurological condition such as CP have poorer motor performance and lower physical fitness in childhood and adolescence than children born full-term. In the preschool years, gross motor deficits have been found to increase from 18 months through 3 and 5 years; that is, the proportion of children with gross motor deficits increased as children matured.5 A recent systematic review of the literature published between 1990 and 2008, describing motor impairments in children born preterm aged 4 to 16 years who did not develop CP, reported pooled prevalence estimates of 40.5% and 19.0% for mild to moderate and moderate motor impairments, respectively.6 This result was consistent, regardless of the standardized measure that was used and age at follow-up of these school-aged children. The prevalence of motor function limitations in this subgroup of children appears to be slightly lower in more recent cohorts3–6; however, the proportion of affected children remains high. Furthermore, children and adolescents born preterm with very or extremely low birth weights have been reported to have lower body mass,7,8 lower anaerobic muscle performance,7 lower fitness levels,8,9 less muscle strength,8,9 slower reaction time,10 poorer coordination,8,10 and lower physical activity levels9 than their full-term counterparts. Recently, motor coordination difficulties, and not the degree of impairment in respiratory function, have been found to be the most powerful predictor of poor cardiorespiratory endurance of 11- to 13-year-old children born preterm without a definitive neurological impairment.8
Some evidence suggests that these differences in developmental outcome in childhood might have their origins in infancy. For example, in one study a significant proportion of infants born preterm, without significant neurological abnormalities, were passive and delayed in the acquisition of antigravity postural control and motor development.11 We believe that these differences reflect sequelae of preterm birth12 (not solely the effect of sleep positioning on transient early motor delays13) and variations in childrearing practices affecting motor development.
Motor performance in childhood is known to be related to childrearing habits,14 which has mostly been studied by comparing practices across different ethnic groups. In infancy, specific handling techniques of black parents from the Caribbean and parents in Canada that exposed infants to postural challenges have been shown to be associated with motor advancement.15,16 In contrast, infants of Asian American parents are frequently calmed and nursed in a supine position17 and these infants display little spontaneous movement early in life.18 In their detailed review of variations in childrearing practices across cultures, Adolph and her colleagues summarize that “[i]n general, cultural factors that augment practice and enrich or intensify stimulation can accelerate [motor] developmental timing; contextual factors that restrict practice and reduce stimulation can delay onset ages.”19(p7) We believe that childrear-ing practices to support early motor development include providing infants with opportunities to develop antigravity postural control and to actively explore their environments. For families with infants and children born preterm, Keller and associates10 stated that they “cannot exclude the possibility that factors such as parental overprotection, fear of deleterious effects of exercise, or impaired exercise performance might have induced hypoactivity during the first years of life”(p665); these childrearing practices might have influenced suboptimal motor performance in mid-childhood among children born early. Others have also speculated that parents of infants born preterm might be more concerned about safety and overall health problems than parents of infants born full-term, thereby restricting habitual physical activity.7
These perspectives are consistent with the phenomena known as “vulnerable child syndrome”20 and “prematurity stereotyping,”21 both of which are associated with cautious overprotection by parents and underachievement by the child. Notably, all of the publications on this phenomenon are from North American authors (see Appendix). Little is known about perceptions of vulnerability of parents of infants born preterm in other world regions. Furthermore, the nature of childrearing practices affecting motor development and the relationship between perceptions of vulnerability and childrearing practices are not known.
While on sabbatical travels, Bartlett had interesting conversations with VanHaastert in Utrecht, the Netherlands, and Bjørg Fallang in Oslo, Norway. Both of these infant researchers believed that the phenomenon of “prematurity stereotyping” or “vulnerable child syndrome” did not occur in their environments to the same extent as has been documented in North America, partly because there is a paucity of research literature from their countries on these topics. Historically, Dutch people have been physically very active, with virtually everyone in the nation owning at least one bicycle. Similarly, Norwegians have traditions for outdoor life, skiing, biking, and hiking. In both countries, children seem to be exposed to high levels of physical activity at a young age; similarly, inclusion of children with disabilities in school and community activities is advocated in both countries. We realized we had an opportunity to conduct a natural experiment. The purpose of our work was to determine differences in parents' perceptions of child vulnerability and their childrearing practices that affect motor development in Canadian, Norwegian, and Dutch sites, as well as to determine the relationship between parents' beliefs about their infants born preterm and their own childrearing practices.
The study was designed as a cross-sectional observational study.
A quota sample of 84 parents of infants born preterm (28 at each of 3 sites) was targeted for recruitment. The quota sampling method was selected to ensure efficient, representative recruitment of infants at risk for motor function limitations across the age range of 4 to 11 months at the time of data collection (age corrected for prematurity); at gestational ages (GA) of 24 to 32 completed weeks of gestation, in keeping with the GA range of those at highest risk4; and at birth weights (BWs) greater than the 5th percentile for GA22 of interest as well as to minimize possible assembly biases across sites (see Table 1). Infants were eligible for this study if their GAs at birth and BWs matched with 1 of the strata in the quota sampling plan. Exclusion criteria included GA at birth greater than 32 weeks, definitive diagnosis of CP, intraventricular hemorrhage (IVH; levels III or IV), neonatal or perinatal stroke, seizures requiring medication, visual abnormalities, auditory abnormalities, and significant metabolic, cardiac, or musculoskeletal abnormalities, thus excluding infants with a high probability of a definitive developmental disability. Infant characteristics are contained in Table 2. The targeted sample size was not obtained; however, 62 infants and their parents were successfully recruited. Infants were not significantly different across the countries with respect to gender, GA, BW, Apgar score at 5 minutes, IVH, or age at the time the data were collected. They were significantly different with respect to presence of minor periventricular leukomalacia (affecting 5 infants in the Netherlands), having been discharged home on oxygen (3 infants in Canada), number of health conditions (more in Canada and Norway), and the number receiving services since hospital discharge (more prevalent in the Netherlands).
Parents were eligible if they were older than 18 years, able to read and comprehend English or Norwegian or Dutch, and without any major psychiatric or health conditions affecting their abilities to care for their children. Participating parents were born in Canada, Norway, or the Netherlands (and at least one of their parents was born in the respective country as well), to attempt to provide samples reflecting Canadian, Norwegian, and Dutch “cultures” as much as possible. All 3 countries currently have significant immigration from people around the globe; our intent was to obtain relatively more homogeneous samples within each country with respect to parental childrear-ing practices. Parents who were not primary caregivers of their infants were not eligible to participate unless the child's caregiver agreed to complete the measure of caregiving practices when they were with the infant. Most caregivers were mothers, with one father each participating in Canada and the Netherlands. Caregiver characteristics are contained in Table 3. Caregivers were not significantly different with respect to age or education, although a higher proportion of parents in Norway had completed university. Prior to recruiting the infant and parent participants, ethical approval was obtained from institutions in Canada, Norway, and the Netherlands. Each parent participant provided written informed consent.
A modification of the Vulnerable Child Scale23 was used to measure parents' perceptions of their infants' vulnerability. This measure has 16 items that reflect parent's concerns about a child's health. Each item is scored using a 4-point Likert Scale from 0 to 3 (0 = “definitely true,” 1 = “mostly true,” 2 = “mostly false,” and 3 = “definitely false”). Items 5 and 9 are reverse-coded. Scores range from 0 to 48, with lower scores representing more vulnerability. Cronbach alpha is reported as 0.75, and the test-retest reliability coefficient over a period of a month was 0.96. Parents with higher education and socioeconomic status perceived their children as less vulnerable than those with lower education and socioeconomic status.23 For our purposes, we replaced the word “child” with “baby” and the item “I feel guilty when I have to punish ______” with “I feel guilty when I have to say 'no' to scold my baby” and renamed this measure the Beliefs About My Baby Scale (BABS). We made these changes to be more meaningful to parents of infants; we also preferred a title that was positively worded.
The childrearing practices of interest in this study are those that capture the opportunities parents provide their infants for the development of antigravity postural control and movement exploration. These are perceived to be the childrearing practices that have the potential to contribute most to early motor development. The Daily Activities of Infants Scale (DAIS) is a discriminative and predictive parent-completed measure of this construct.24 Dimensions were generated by taking and categorizing, through consensus, approximately 1300 photographs of typical daily activities of 17 Canadian families comprising parents and infants aged between 4 and 11 months. Nine dimensions were generated initially, which were refined after pilot testing. The DAIS currently has 8 dimensions (feeding, bathing, dressing, carrying, quiet play, active play, outings, and sleeping). Each dimension is scored on a 3-point ordinal scale from least (A) to most (C) opportunity for development. Each level is supported by illustrative photographs and additional photos are provided to assist parents in determining the level. To complete the measure, parents are asked to record the predominant activity in each 15-minute block over a 24-hour period by first identifying the dimension, and then the level of the dimension, that best matched the activity performed by the parent-infant dyad. Reliability and validity testing was subsequently conducted with 50 parents of infants born preterm (25 girls and 25 boys). Data collection on 1 day was found to be representative of data collected over 3 consecutive days. Evidence of construct validity was supported by determining that infants aged 4 to 7 months obtained significantly lower total DAIS scores than infants aged 8 to 11 months (t = −6.80, df = 41, P < .001). Construct validity was also established by determining that age and DAIS scores obtained part correlations of 0.43 and 0.20 with scores on the Alberta Infant Motor Scale (AIMS).25 Thus, the DAIS is associated with scores on the AIMS, over and above the effect of age. Interrater and test-retest reliability has been established between parents and 1 of 3 physical therapists, and within parents over a 2-week period for the total score (ICC > 0.75).
As indicated earlier, each dimension (with the exception of sleeping) is scored as either A (1 = least opportunity for antigravity postural control or movement development), B (2 = middle opportunity), or C (3 = most opportunity). A total score is established by multiplying the value associated with the level by the number of 15-minute intervals in each dimension, summing across dimensions. Data can be analyzed in several ways; in this work, we use the total DAIS score, as well as individual dimension scores.
Demographic data were also collected about the participating infants and their families; those data are presented in Tables 2 and 3. All measures that were completed by parents were translated into Norwegian and Dutch, and back translated to ensure that the correct meanings were maintained, prior to data collection.
After obtaining informed consent, a coinvestigator or student collaborator obtained information from the infant's medical record and then arranged to have the other forms mailed to the family when the child had reached the age determined by the quota sampling strategy. This person contacted the primary caregiver by phone to clarify the instructions for completion of the data collection forms. With respect to the DAIS, parents were asked to score their activities every 2 hours, thinking back on the categories that best matched what they did with their infants over eight 15-minute intervals. Parents were provided with stamped addressed envelopes for return of all data forms.
First, descriptive data on the BABS and DAIS were established. A one-way analysis of variance (ANOVA) was conducted to compare the total scores on the BABS across the 3 countries. The proportions of 15-minute intervals recorded on the DAIS over the 24-hour period were first plotted in the form of box-plots and inspected visually to determine outliers. A one-way ANOVA was conducted comparing the DAIS total and dimension scores across the 3 sites. Finally, a regression analysis was conducted with the BABS as the independent variable, number of health conditions and education as covariates, and DAIS score as the dependent variable.
An alpha value of 0.10 was set a priori for this exploratory work. A total sample of 62 participants yields a power of 0.71 to detect a “medium” effect (f = 0.30) using a one-way ANOVA26 (ie, this study is slightly underpowered, given our difficulties with recruitment). The BABS and DAIS data were treated as interval level, because they meet the assumptions of representing an underlying continuum and yielding a normal distribution.27
Descriptive data on the BABS and DAIS are contained in Table 4. BABS scores were significantly different among the countries (F = 6.45, df = 2, P = .003), with parents in the Netherlands perceiving their infants as being more vulnerable than parents in either Canada or Norway (Tukey's Post Hoc Test, P < .001). For the DAIS scores, we first checked to make sure that parents completed a total of close to 96 boxes over the 24-hour period. The Figure contains box plots of the ratio of the number of completed boxes divided by 96. A ratio of 1 indicates that parents completed exactly 96 boxes. A ratio higher than this indicates that parents completed more than 96 boxes; a ratio lower than this indicates that parents completed fewer than 96 boxes. Three significant outliers were detected: 2 were in Canada (IDs 10 and 11) and 1 was in Norway (ID 49). These were deleted from the database for subsequent analysis so that they would not skew the results. The one-way ANOVA (using our exploratory alpha level of 0.10) revealed significant differences among the countries for carrying (F = 4.82, df = 2, P = .01), quiet play (F = 2.28, df = 2, P = .07), and sleeping (F = 3.89, df = 2, P = .03). Parents in the Netherlands reported lower carrying scores than parents in Canada (Tukey's Post Hoc Test, P = 0.01). Parents in the Netherlands reported lower quiet play scores than parents in Canada (Tukey's Post Hoc Test, P = .07). Parents in the Netherlands reported higher sleeping scores than parents in Canada (Tukey's Post Hoc Test, P = .02). In terms of total DAIS scores, there were no significant differences among the 3 countries.
The regression analysis with the BABS as the independent variable, and number of health conditions and education as covariates, and DAIS score as the dependent variable was not statistically significant overall. Only education reached statistical significance (P = .08) with a standardized beta coefficient of −0.24 (ie, parents with higher educations reported lower DAIS total scores).
Because this work has been framed in an exploratory context, an additional regression analysis was conducted with the DAIS dimension score that was most different among the countries: carrying. The same model was run, and in this case, the model was significant within our set alpha level (P = .09). Eleven percent of the variation in carrying score was statistically supported by the BABS score (P = .04, standardized beta coefficient = 0.27) and education (P = .08, standardized beta coefficient = −0.24). Parents with less perception of their infants' vulnerability, and those with less education, provided more opportunities through their carrying activities for the development of antigravity postural control.
Finally, we were interested in the highly statistically significant variation in availability of services among the 3 countries. Results of t tests on both the BABS and the DAIS scores between those receiving services and those not receiving services for the combined sample are contained in Table 5. Interestingly, parents who received therapy services had greater perceptions of their infants' vulnerability than parents not receiving services. There was no statistically significant difference in DAIS scores; however, there is a small trend for those receiving services to have lower DAIS scores. To understand the sources of variation in perceptions of vulnerability, we compared GA, BW, and number of health conditions between those receiving services and not through independent t tests. Only number of health conditions was significantly different (t = 3.30, df = 56, P = .002), with those receiving services having fewer health conditions (mean = 1.0, SD = 1.1) than those not receiving services (mean = 2.1, SD = 1.3). The proportion of infants with IVH and having been discharged home on oxygen were compared between those receiving services and not using chi-square. No significant differences were detected. Periventricular leukomalacia was not included in this post hoc analysis, because all 3 infants were from the Netherlands, and all received services. Finally, we investigated the correlations between the BABS scores and GA, BW, and number of health conditions using Pearson's correlation coefficient and between the BABS scores and IVH and discharged home on oxygen using the point biserial correlation. No significant correlations were obtained.
The results associated with the primary purpose of this study were not anticipated. First, given the predominance of the prematurity stereotyping literature from North America, we anticipated that Canadian parents might perceive their infants to be more vulnerable than parents in either Norway or the Netherlands. In fact, in this study, parents in the Netherlands perceived their infants to be more vulnerable. Second, although the total DAIS scores were not significantly different among the 3 countries, parents in the Netherlands reported lower carrying and higher sleeping scores than parents in Canada, with parents in Norway being in the middle of these 2 countries. These results are not attributable to possible differences in the actual vulnerability of the children in terms of their GAs at birth, BWs, or number of health conditions or the ages of the children at the time they participated in the study (ie, selection bias does not explain these results). Although parents in the Netherlands had greater perceptions of vulnerability than parents in Canada and Norway, there was no association between perceptions of vulnerability and childrearing practices supporting early motor development (controlling for number of health conditions and parental education) when looking at the total DAIS score. However, when looking at the DAIS dimension score of carrying, 11% of the variance in how parents carried their infants was attributed to both perceptions of vulnerability, in the expected direction, and education, in a direction that was not expected. In interpreting these results, recall that the DAIS total and section scores are composed of both amount of time and extent of challenge. These results therefore provide some support for the hypothesis that parents' beliefs about their children's vulnerability contribute in some way to their childrearing practices to support early motor development. A surprising finding was the result that parents who were receiving therapy services perceived their infants as more vulnerable than those not receiving therapy services.
Despite the lack of definitive information on the variable reasons that children and families received services, as well as lack of information on the frequency, intensity, duration, focus, and setting of intervention, the results of this study lead us to wonder if receiving therapy services is as uniformly beneficial (at best) or benign (at worst) as we commonly assume. Is it possible that the mere fact of receiving services actually contributes to parents' perceptions of their children's vulnerability? Is it possible that therapy services contribute to this phenomenon by focusing on deficits and possible adverse outcomes rather than taking a strength-based perspective? Does a focus on deficits actually contribute to higher perceptions of vulnerability? Conversely, might it be possible that taking a strength-based perspective avoids adverse outcomes associated with prematurity stereotyping? What is the content and focus of therapy that leads to optimal outcomes of these high-risk infants?
In a Cochrane review of the randomized (n = 6) and quasi-randomized (n = 10) intervention trials conducted within the first 12 months of life with infants born preterm published between 1966 and February of 2006, little evidence was found for the effectiveness of early interventions on motor outcomes in the short (birth to 2 years), medium (3 to <5 years), and long (5–17 years) terms.28 The authors concluded that “[t]he heterogeneity between early developmental intervention programs in regard to content, focus and intensity limit the conclusions that can be drawn from this review.”28(pp18-19) They recommended that future work should target interventions to address the needs of the infant and family more specifically. A more recent systematic review including literature up to June 2008 focused on interventions involving parents (eg, teaching parenting skills and/or involving parents in the hospital care of the infant) found some evidence of effectiveness; however, effects were found to be greater (and sustained longer over time) on cognitive rather than motor outcomes.29 These authors concluded “[i]t remains of great importance to identify effective interventions to improve the long-term outcomes of this vulnerable population and their families.”29(p349)
Along these lines of thinking and recommendations, a recently published study focused intervention between hospital discharge and 6 months corrected age on specific suggestions to parents to support their infants' functional competence, guided by infants' behavior, and to adjust the environment according to the infants' needs to enhance postural control and successful infant explorations.30 This approach resulted in higher motor competencies at 24 months than those receiving regular care. Importantly, the intervention was tailored to each parent-infant dyad by first providing parents with information about each infant's unique development and then using anticipatory guidance to suggest the functional abilities that would likely emerge next.30 Our recommendations for future research, described next, are entirely consistent with this approach.
We believe that future work should consider multiple aspects to support intervention, and should be longitudinal instead of cross sectional, as reported here. It would be useful to recruit a sample with greater representation of all educational levels so that the role of education could be more fully explored, and more strategies put in place to support families. A measure of parents' perceptions of their infants' vulnerability based on motor competencies should be developed. A more refined instrument may assist in illuminating potential relationships between parents' perceptions of their infants and their childrearing practices to support the early functioning of these infants. Reliability of this new scale should be established. Work also needs to be conducted to assist with interpretation of the DAIS scores. What values are typically obtained from parents of infants born at term, and how do these scores compare with scores from parents higher risk infants born preterm? One variable that was not considered in the current work was birth order. Future work should consider parents' experiential knowledge of raising other children, either born full-term or preterm, and potential effects on perceptions of vulnerability. In addition, the potential determinants of parents' perceptions of vulnerability and their childrearing practices to support motor development logically need to be linked to infant motor development. Given our fundamental belief that the manner in which parents physically interact with their infants has the potential to either enhance or hinder early physical activity, investigating the potential effects of an educational package using the DAIS is warranted. Using parent-friendly, pictorial materials such as the AIMS25 and the DAIS24 together, along with systematic observations of the unique characteristics of the infant, parent's perceptions of infant vulnerability relating to motor competencies, and the environment in which the infant is developing,31 has the potential to assist parents in many ways. This package of materials might help parents understand their infants' current motor repertoire, anticipate the motor behaviors that will likely emerge next, explore the “fit” between their childrearing practices to support motor development as measured by the DAIS and their infants' motor competencies and unique characteristics, engage their infants in more challenging DAIS items on a routine basis throughout their daily activities, and modify the environment in which the child lives to support development of antigravity postural control and movement exploration. The feasibility and acceptability of this comprehensive approach is currently being explored on a longitudinal sample of infants from 4 to 11 months of age. A focus group will be held at the end of the pilot work to ascertain how to make this package most engaging to parents of infants at risk for developmental disabilities. This approach is consistent with recommendations by others who have highlighted the importance of a strengths- and process-based approach to support the parent-infant relationship and the infant's emerging functions.30
We recognize significant limitations in this study. First, we were not successful in recruiting our target sample size within the funding period of this study. This work can only be seen as preliminary and exploratory. Second, the aspects of vulnerability captured in the BABS may be too generic and not related specifically to motor competence, as indicated earlier. Third, some parents had difficulty in scoring the DAIS, which led to 3 cases being excluded from the analysis. These 3 parents had relatively lower levels of education (1 in Norway had not completed high school and 2 in Canada had just completed high school). More detailed instruction needs to be considered with some parents if the DAIS is used in future work. Fourth, we did not have access to uniform data to ascertain actual vulnerability with respect to developmental status at the time the data were collected. As a result, our query about the potential effect of participation in therapy as contributing to perceptions of vulnerability is only speculative, but in our opinion, a possibility that is worth thinking about.
Despite the inherent limitations of this study, we did not find any support for the notion that prematurity stereotyping is exclusively a North American phenomenon. We have some evidence that parents' perception of their children's vulnerability contributes to opportunities they provide these infants to develop antigravity postural control through the ways in which they carry their infants. The finding that parents whose infants were receiving therapy services perceived their infants as more vulnerable suggests to us that we might need to be vigilant about potential harmful effects of therapy services. Our results, in the context of recent literature, suggest that future research should investigate strength-based and relationship-focused interventions to support infant motor development, childhood motor performance and fitness, and long-term health in this high-risk group of those born preterm without definitive neurological conditions such as CP.
The authors thank Jeanne van der Burgt and Katerina Steiner (the Netherlands) and Unn Inger Moinichen and Marthe Eggesvik (Norway) for their assistance with data collection and Inge-Lot van Haastert for ongoing conversations.
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APPENDIXArticles on Prematurity Stereotyping and Vulnerable Child Syndrome
Allen EC, Manuel JC, Legault C, Naughton MJ, Pivor C, O'Shea TM. Perception of child vulnerability among mothers of former preterminfants. Pediatr. 2004;113:267–273.
Green M. Vulnerable child syndrome and its variants. Pediatr Rev. 1986;8:75–80.
Perrin EC, West PD, Culley BS. Is my child normal yet? Correlates ofvulnerability. Pediatr. 1989;83:355–363.
Shonkoff JP. Reactions to the threatened loss of a child: a vulnerablechild syndrome, by Morris Green, MD, and Albert A. Solnit, MD, Pediatr. 1964; 34:58–66. Pediatr. 1998;102:239–241.
Stern M, Hildebrandt KA. Prematurity stereotype: effects of labeling onadults' perceptions of infants. Dev Psychol. 1984;20:360–362.
Stern M, Hildebrandt KA. Prematurity stereotyping: effects on mother-infant interaction. Child Dev. 1986;57:308–315.
Stern M, Hildebrandt KK. Prematurity stereotyping by mothers ofpremature infants. J Pediatr Psychol. 1988;13:255–263.
Stern M, Hildebrandt Karraker K. Modifying the prematurity stereotype:the effects of information on negative perceptions of infants. J SocClinical Psychol. 1989;8:1–13.
Stern M, Hildebrandt Karraker K. Modifying the prematurity stereotypein mothers of premature and ill full-term infants. J Clin Child Psychol. 1992;21:76–82.
Stern M, Hildebrandt Karraker K, Meldrum Sopko A, Norman S. The prematurity stereotype revisited: impact on mothers' interactionswith premature and full-term infants. Infant Ment Health J. 2000;21:495–509.
Stern M, Karraker K, McIntosh B, Moritzen S, Olexa M. Prematu-rity stereotyping and mothers' interactions with their premature andfull-term infants during the first year. J Pediatr Psychol. 2006;31:597–607.
Thomasgard M, Metz WP. The vulnerable child syndrome revisited. Dev Behav Pediatr. 1995;16:47–53.
Canada; childrearing; health status; infants; mothers/psychology; Norway; premature; premature infants; social perception; the Netherlands
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