Cognitive Development of Very Low Birth Weight Children from Infancy to Pre-school Age

(abstract of the doctoral dissertation)


The survival of preterm born infants has increased but the prevalence of longterm morbidities has still remained high. Preterm born children are at an increased risk for various developmental impairments including both severe neurological deficits as well as deficits in cognitive development. According to the literature the developmental outcome perspective differs between countries, centers, and eras. Definitions of preterm infant vary between studies, and the followup has been carried out with diverse methods making the comparison less reliable. It is essential to offer parents uptodate information about the outcome of preterm infants born in the same area. A centralized followup of children at risk makes it possible to monitor the consequences of changes in the treatment practices of hospitals on developmental outcome.


This thesis is part of a larger regional, prospective multidisciplinary followup project entitled “Development and Functioning of Very Low Birth Weight Infants from Infancy to School Age” (PIeniPAinoisten RIskilasten käyttäytyminen ja toimintakyky imeväisiästä kouluikään, PIPARI). The thesis consists of four original studies that present data of very low birth weight (VLBW) infants born between 2001 and 2006, who are followed up from the neonatal period until the age of five years.


The main outcome measure was cognitive development and secondary outcomes were significant neurological deficits (cerebral palsy, CP, deafness, and blindness). In Study I, the early crying and fussing behavior of preterm infants was studied using parental diaries, and the relation of crying behavior and cognitive and motor development at the age of two years was assessed. In Study II, the developmental outcome (cognitive, CP, deafness, and blindness) at the age of two years was studied in relation to demographic, antenatal, neonatal, and brain imaging data. Development was studied in relationship to a fullterm born control group born in the same hospital. In Study III, the stability of cognitive development was studied in VLBW and fullterm groups by comparing the outcomes at the ages of two and five years. Finally, in Study IV the precursors of reading skills (phonological processing, rapid automatized naming, and letter knowledge) were assessed for VLBW and fullterm children at the age of five years. Prereading skills were studied in relation to demographic, antenatal, neonatal, and brain imaging data.


The main findings of the thesis were that VLBW infants who fussed or cried more in the infancy were not at greater risk for problems in their cognitive development. However, crying was associated with poorer motor development. The developmental outcome of the present population was better that has been reported earlier and this improvement covered also cognitive development. However, the difference to fullterm born peers was still significant. Major brain pathology and intestinal perforation were independent significant risk factors for adverse outcome, also when several individual risk factors were controlled for. Cognitive development at the age of two years was strongly related with development at the age of five years, stressing the importance of the early assessment, and the possibility for early interventions. Finally, VLBW children had poorer prereading skills compared with their fullterm born peers, but the IQ was an important mediator even when children with mental retardation were excluded from the analysis.

The findings suggest that counseling parents about the developmental perspectives of their preterm infant should be based on data covering the same birth hospital. Neonatal brain imaging data and neonatal morbidity are important predictors for developmental outcome. The findings of the present study stress the importance of both shortterm (two years) and longterm (five years) followups for the individual, and for improving the quality of care