Dept. of Psychology, Lund University, S-22000, Lund, Sweden. E-mail:Karin.Stjernqvist@psychology.lu.se

During the last decade, several studies have reported poor school performance in extremely preterm infants (EPT). According to this body of research, developmental outcome is related, among other things, to maternal education and family income and research in different countries indicates that extremely preterm infants are over-represented in socially disadvantaged families. It is therefore important that follow-up studies be population-based and be conducted in countries with different socio-economic structures. The aim of this Swedish study was to compare the health, cognitive and behavioural development and school achievement of extremely preterm infants at 10 years of age with a matched sample of 10-year old children, who were born healthy and were full-term (FT).

Methods

In a south Swedish town, 32,120 infants were born during a two-year period 1985 to 1986. One hundred and twenty-one infants (0.4%) were reported live born before the 29th gestational week. Sixty-five infants (50%) survived up to the age of 10 years. (See table 1) The catchment area has one regional tertiary centre and 10 community hospitals, 8 level II and 2 level I hospitals. The children were recruited in the pre-surfactant era. When the Extremely Preterm children were 10 years old, the parents were invited to participate in the follow-up study. Sixty-one of the 65 children, participated in the ten-year follow up study. Parents of full term children from the same region of the same sex and with the date of birth closest to the study child were approached to participate in the study.

The children were assessed with a test battery by a psychologist who was blind to group affiliation. To assess their cognitive abilities, the Wechler Intelligence Scale for Children, WISC-III, was used. To assess visual-motor abilities, the Developmental Test of Visual-Motor Integration, VMI, was used and the standard score was calculated. A paediatrician reviewed the children’s medical record. The children were assessed at the regional centre and were accompanied by at least one parent, usually the mother. Behavior and attention were assessed by questionnaires filled in by the parents. The Child Behavior Checklist, CBCL, was used to assess behavioral development. (According to Swedish norms, the cut-off score for manifest behavior problems is 30).). The Home Situation Questionnaire, revised, HSQ-r, was used for measure evidence of attention-deficit hyperactive disorder (ADHD). A score above 2 in more than 8 of the 14 items exceeds the Diagnostic Criteria from DSM-IV cut-off for a diagnosis of ADHD. The parents also completed a questionnaire about their socio-economic background, the family composition and the child’s health. The parents were asked for their consent to allow the Teacher’s Report Form (TRF) to be sent to the child’s classroom teacher.

At the time of follow-up, the EPT children were 10.5 years of age, while the FT children were10.6 years old. All scores were calculated based on the child’s chronological age. The extremely preterm group and the full term control-group were similar in family composition, number of siblings and immigrant status.

Ten-Year Outcomes

Health

Ten per cent of the EPT-children had small intraventricular haemorrhages (IVH) and 11% had big bleeds as assessed by ultrasound in the newborn period. Four children, all with IVH grade III or IV, had cerebral palsy and 3 of these also had visual impairments, and 1 child had a severe hearing impairment. The EPT children were on average 5 cm shorter, 142.2 cm for the EPT children as compared to 147.0 cm for the FT children. The EPT children also had lower weight, on average 4 kg, 33.4 (7.6) kg vs. 37.6 (7.2) kg for the FT children (p<0.01) and had a smaller head circumference, 53.1 (1.8) cm vs. 54.2 (2.1) cm, than the FT controls (p<0.05). There were no differences between the groups in visits to a physician during the last twelve months. The need for visual correction with glasses was greater among the EPT children, 25 vs. 7 (p<0.001).

Development and school achievement

The EPT children had a mean IQ score of 90 (SD, 15), while the FT children had a mean IQ score of 106 (SD, 15) (p<. 0001). (See table II) On the test of Visual Motor Integration, the EPT children had a mean score of 93.3 (SD, 12.2), while the Full-term group had an n average score of 109.6 (SD, 14.2) (p<. 0001). On both tests the differences between the groups corresponded to approximately one standard deviation. The IQ results and the results on the VMI test for the EPT children did not correlate with birthweight, gestational age, and birthweight for gestational age or perinatal events such as ventilator treatment, bronchopulmonary dysphasia (BPD) and length of hospitalisation.

Thirty-eight percent of the EPT children performed below grade level at school. (See table III) Thirty-two percent had general behavior problems and 20% had attention deficit with hyperactivity disorder as compared to 10% and 8%, respectively in the FT group.

Ninety-two per cent of the EPT children vs. all FT children were attending school within the normal school system. Thirty percent of the EPT children and 1.6% of the FT children received special education (p<0.001) and thus 66 % of the EPT children vs. 95% of the FT children (p<0.001) were in mainstream education at an age-appropriate level without extra support. Thirty-eight percent of EPT children and 12% of the FT children performed below grade level.

Behaviour

As measured by the CBCL, the EPT children had more general behaviour problems than the FT children. (See table IV) A comparison of the mean scores on the CBCL, yielded significant differences between the EPT and FT scores, 26.1 (SD, 18.2) v. 15.5 (SD13.6) (p<. 001). Thirty two percent of the EPT children and 10% of the FT children met the criteria for manifest behaviour problems (p<0.01). Twenty per cent of the EPT and 8% of the FT children (p<0.05) had ADHD, according to DSM-IV criteria.

NBAS and 4 and 10 year outcome

A subgroup of 17 EPT-children has been followed prospectively since birth. At term, when the EPT children were 10-16 weeks old, the NBAS was performed. At 4 years of age they were tested with the Griffith’ Scales and at 10 with the WISC —III. The correlation between the NBAS Social-Interactive cluster and DQ at 4 years was 0.42 (p<0.05) and the IQ at 10 years was 0.62 (<0.01)

Healthy children with cognitive and behavioural problems

This is the first long-term follow-up study of school achievement of EPT children in the Scandinavian countries. Despite the fact that the majority of the EPT children had good health and were being raised in a low-risk environment, their IQ scores were approximately one standard deviation lower than those of the FT controls. Forty-three per cent of the EPT children had a cognitive development score in the subnormal range, IQ<85, which was reflected in their academic achievement. More than one third of the EPT children performed below grade level at school and 30% of the children who attended mainstream schools received special education. More than half of the EPT children with IQs below 70 were not previously identified as mentally retarded either by parents or by their teachers. They went to mainstream schools and some of them did not even receive special education. Thus there is reason to assume that some EPT children do not have adequate support at school. Most teachers did not know that the pupil was a preterm child, since the parents did not consider the preterm birth as an event that might have long-term impact on the child’s cognitive ability.

It is interesting that the infants early ability to orientate inanimate auditory and visual stimuli and to the human voice and face in the newborn period is associated with later cognitive development. These results are under further investigation.

We did not find any correlation between gestational age or birthweight and IQ or the visual motor functioning. It seems that extreme prematurity per se, displaces the normal variation curve for intelligence approximately one standard deviation below. There is already considerable brain development taking place during the gestational period of 24 to 40 weeks. The neonatal intensive care experience for these children took place when changes were being introduced to reduce stimulation but still improvements in stimuli adaptation must be considered. Other possible causes of these deficits could be nutritional factors, instability in brain perfusion and oxygenation.

We found a relatively low incidence of attention deficit hyperactivity disorder, ADHD, in the group of EPT children (20%) as compared to other studies. For the FT control group the prevalence in our study was 8%, which is in accordance with the figures for the general Swedish population.

Almost every third EPT child compared to every tenth FT child in the present study met the criteria for manifest psychiatric disorders. The behavioural problems could partly be understood as symptoms of minor neurological sequelae but also can be understood as a psychological consequence of parental insecurity in raising a very preterm child. Many studies have reported difficulties in mother and child interaction, during the child’s first year, as a result of the unclear communication signals the EPT infants send to their caretakers compared with fullterm healthy children. The EPT child is also often a difficult child during the first year of life, with insufficient self-regulation leading to feeding and sleep disorders. Later in development, parents might have difficulties in meeting the child’s needs at his or hers developmental level, since many children might be less talented than expected in the family compared with, for example, the siblings. It is however important to stress that 85% of the EPT children are developing within the normal range (> -2SD), but with lower IQ’s than their peers, and that every forth child has an appropriate level of cognitive development and every fifth child performs above grade level at school.

It is obvious that interventions at different levels are needed to support EPT children’s development. Besides continuous improvements in medical care, more directed individualized developmental care in the neonatal period is needed. Long-term intervention programmes aiming to give parents a better understanding of the characteristics of EPT children’s development are also warranted. This could encourage parents to become better advocates for their children. The increased understanding of the child’s needs and their capacities might improve their development and diminish behavioural problems. At a later age, individualized care plans in school settings seem necessary.

(References are available from the author)

Table I

Perinatal data for extremely Preterm (EPT) and Fullterm (FT) infants

^* IVH, interventricular haemorrhage according to the grading of Papile (7).

Table II

Test Results of Cognition for Extremely Preterm (EPT) and Fullterm (FT) children

Table III

School performance of Extremely Preterm (EPT) and Fullterm (FT) children

Table IV

Results of Child Behavior Checklist for Extremely Preterm (EPT) and Fullterm (FT) children

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