Background/Aim: During the past two decades, major advances in maternal-fetal medicine, neonatology, and the development of regionalized perinatal care have resulted in dramatic increases in survival rates, by more than 60%, of extremely immature (EI) infants born at less than 26 completed weeks of gestation, creating a new infant population. Studies of school-age outcomes in children with an extremely low birth weight of < 1000 g, born in the1980s, indicated that these children had a substantially high prevalence of low-severity neuropsychological deficits, behavioral problems, and difficulties at school. Information on school-age outcomes of extremely preterm children born in the 1990s is sparse, and mainly restricted to the neurobehavioral and developmental outcome. The aim of this research was to investigate the comprehensive neurological, developmental, functional, and mental health status and health care needs of children born at 23-25 weeks of gestation in the 1990s, allowing a total view of the child in the context of the family, his peers, school, and the health care system. The ultimate aim was to obtain a clearer understanding of the functional capacities of these vulnerable children and the possibilities of ameliorative interventions, as a basis for planning and provision of services for this growing population. Methods: We studied 11-year-old children born from 1990 through 1992 before 26 completed weeks of gestation in all of Sweden. All had been evaluated at a corrected age of 36 months. Of 89 eligible children, 86 (97%) were studied at a mean age of 11 years. An equal number of children born at term served as controls. The following methods were used: 1) well validated, mailed questionnaires filled out by the parents, class teachers and the children themselves; 2) structured interviews were conducted with a parent or a primary caregiver; 3) review of pediatric case records and records from other specialist health care services; and 4) anthropometric measurements (length, weight, head circumference and body mass index) from birth to 11 years of age. The following domains were explored: current health status, growth attainment, mental health assessment, emotional well-being, adaptive functioning and social competencies, school performance, executive functions, and learning and language skills. Relations of socioeconomic background and of environmental and perinatal risk factors to the long-term outcome were evaluated. Results: EI children compared with the controls had significantly higher rates of specific diagnoses or disabilities including neurosensory impairment (15% vs 2%, respectively), asthma (20% vs 6%), poor motor skills (26% vs 3%), poor visual perception (21% vs 4%), poor learning skills (27% vs 3%),poor adaptive functioning (42% vs 9%), and poor academic performance (49% vs 7%). As a consequence of these disabilities, significantly more EI children than controls had chronic conditions, which included functional limitations (64% vs 11%), compensatory dependency needs (59% vs 25%), and services above those routinely required by children in general (67% vs 22%). Regarding growth attainment, EI children had significantly lower values for all three growth parameters (length, weight and head circumference) than the controls at 11 years. They showed a sharp decline in weight and height z scores up to 3 months’ corrected age, followed by good catch-up growth in both weight and height up to 11 years. EI children did not exhibit catch-up growth in head circumference after the first 6 months of life. Preterm birth and parental height were significant predictors of 11-year height, and group status (prematurity) correlated strongly with head circumference. Our results also suggest that the EI children had a significantly greater risk for poorer mental health and poorer emotional well-being than the control participants, including internalizing (anxiety/depression, withdrawn behavior and somatic complaints), and attention, social, and thought problems. No differences in externalizing problems were found between the EI cohort and controls. Multivariable analyses disclosed a number of significant predictors of behavioral adjustment: group status (EI vs control), family function, social risk, male gender, and presence of a chronic medical condition. Concerning school performance, more than half (59%) of our EI cohort were experiencing school difficulties and 15%, compared with 5% of the control children were attending special schools or having full-time special education. Despite fewer adaptive skills in the EI cohort these children were not different from the controls in respect to being happy and being positively adjusted in their day-to-day life. Compared with controls, EI children had a significantly increased risk for executive dysfunctions in most of the areas assessed (Attention control and Attention switching, Hypoactivity, Planning/organizing, and Working memory). EI children were also at increased risk for deficient skills in language tasks (comprehension, communication, and expression) and in the four standard measures of learning skills (reading/writing, math, general learning, and coping in learning). However, only a relatively small number of EI children exhibited severe impairments in executive or non-executive skills. Multivariate analyses revealed that prematurity, executive dysfunction and male gender were associated with poor learning skills. Conclusions and implications: Children born extremely immature have significantly greater health problems and special health care needs that require ongoing services through the school years. However, it is notable that very few children have severe impairments that curtail major activities of daily living. The overall results of this study are reassuring. Despite having an increased risk for mental health problems, executive dysfunctions and school difficulties, 85% of the EI children were in the mainstream schools and a majority were not having major adjustment difficulties. In terms of growth, most of our EI children showed good catch-up in late childhood and were within 2SD of their mean midparental height at 11 years of age. Although biological immaturity is associated with an increased risk for a substantial number of behavioral/emotional problems, improvement of the modifiable environmental factors will benefit the outcome in EI children. We also believe that knowledge of the course of development of psychopathological conditions from early childhood to adolescence and beyond is crucial for identifying the need for intervention and prevention strategies. Thus when there is evidence to suggest neuropsychological and behavioral or emotional problems, early identification and preventive measures might help families to manage these from an early stage. Our findings further suggest that current preterm follow-up programs might benefit from the addition of psychological and family services to traditional neurodevelopmental assessments, especially in the neonatal period and first years of life.