Cognitive and behavioural outcomes following very preterm birth
Introduction
A timely report by the Nuffield Council on Bioethics examined the complex ethical and practical decisions clinicians increasingly face regarding the intensive care of extremely preterm (EPT) babies.1 This publication is a testament to the vast advances in neonatal care and the marked improvement in survival of babies born at the limits of viability. As increasing numbers graduate from intensive care nurseries, there is warranted concern regarding the future health and well-being of these survivors and an increasing interest in the long term sequelae of prematurity. This paper reviews research relevant to the cognitive and behavioural outcomes of very preterm (VPT) children in middle childhood and considers methodological issues pertaining to outcome monitoring in this population.
Section snippets
Outcome assessments in middle childhood
Although many studies assess outcome at 2 years, it is important to monitor progress beyond this point given the transient or evolving nature of deficits in infancy and the poor predictive validity of infant tests. Whilst the authors of early studies sought to catalogue the severe neurological and sensory disabilities associated with VPT birth, recent research has highlighted a range of more subtle deficits and has shown that the nature of impairment may be changing.2 Cognitive and behavioural
IQ in middle childhood
Researchers have typically studied population-based cohorts of children to define and quantify outcomes for VPT children. As these studies are necessarily large and frequently have limited time and resources with which to assess survivors, outcomes measures have typically comprised an assessment of global cognitive function. The need for objective measures has led to the widespread use of standardised intelligence (IQ) tests as indicators of outcome. IQ tests are psychometric measures that
Behaviour and psychopathology
VPT children are also at greater risk for long term behavioural and emotional sequelae. These outcomes are relatively difficult to compare as the measures used are more diverse than IQ tests. Assessments are usually conducted through self-reports or parental questionnaires and corroborative information from teacher questionnaires may be incorporated as multi-informant information is emphasised for DSM-IV/ICD-10 categorisation. Information can also be obtained from diagnostic interviews, but
How should we report outcomes?
Variability in outcomes may be attributed to variations in study quality that reflect differences in population definitions, the application of comparator data and the selection of outcome measures. An appreciation of study methodology is important in interpreting results and a number of methodological considerations are noted briefly below with recommendations for improving the reporting of outcomes.
Summary and conclusions
There is no question that VPT birth is a major reproductive risk for cognitive and behavioural sequelae, even in children without significant NSI. Whilst VPT children have group mean IQ scores within the normal range, these are significantly lower than their term peers. Cognitive outcome is most compromised in those born at <33 weeks in whom IQ decreases by an average of 1.5–2.5 points for each decreasing week of gestational age. VPT children appear to have the poorest performance on tests of
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