Due to marked advances in neonatal intensive care it had been found that, survival
rates of preterm infants had been improved. But improvements in survival have
not been accompanied by proportional reductions in the incidence of disability
in this population. Thus, survival is not an adequate measure of success in
these infants who remain at high risk for neuro-developmental and behavioral
morbidities. There is now increasing evidence of sustained adverse outcomes
into school age and adolescence, not only for ELBW infants but for infants born
late preterm (Stephens and Vohr, 2009).
Compared with their classroom peers, preterm children may have cognitive and
neurological impairment at school age (Marlow et al.,
2005). On exam, 10-11% of low birth weight infants have neurological soft
signs, a twofold increased risk compared with their normal birth weight analogues.
Soft signs are defined as deviations in speech, balance, coordination, gait,
tone, or fine motor or visual motor tasks that do not signify localized brain
dysfunction. These soft signs are associated with an increased the risk of subnormal
IQ, learning disabilities, attention deficit disorder and internalizing and
externalizing behaviors at 6 and 11 years (Breslau et
Children who were born preterm are at risk for reduced cognitive test scores
and their immaturity at birth is directly proportional to the mean cognitive
scores at school age. Preterm-born children also show an increased incidence
of ADHD and other behavior-related disorders (Bhutta et
We hypothesized that children delivered at preterm have lower IQ and affected
general cognitive and behavioural functions, so this study is designed to examine
the IQ, general cognitive and behavioural outcome at school age in children
born at term and those who are preterm.
MATERIALS AND METHODS
This is a cross sectional, nested, case control study, carried out in Damietta
primary schools. The principles and technique of randomization and selection
were followed. Informed consent was obtained from every parent of the student
for participation in the study. Measures to guarantee confidentiality on handling
the database and questionnaire forms were arranged.
Sample size and randomization technique: The total number of schools
is 80 schools: 70 public schools, 4 language school and 6 private schools. The
total number of pupils in primary schools was 42824. The primary schools were
divided into three categories, public school, language school and private school
and randomized selection of the targeted schools were done by lottery method.
Our target population was all children in Damietta primary schools. All children
who were delivered at preterm were selected and systematic randomization of
children who were delivered at full term (every ten) was done. The study included
766 children: 206 children who were delivered at preterm and 560 children were
delivered at full term (four children of them were excluded as they were reared
in another country and the other one was excluded because he has diabetes mellitus)
so full term children were 556. Students were divided into two groups: Group
A: Jealthy children born at term. Group B: Healthy children born at preterm.
The study was conducted during the period from January 2010 to August; 2011.
Several visits on scattered days to targeted schools were done on a period of
about 14 work months. The Director of the primary school was first met to tell
him about the idea of the research and to ask about a suitable quite room to
apply the Binet intelligence test. During these visits the researcher moved
freely in the different classrooms of the schools observing the different activities
of the students. Self-administered questionnaires were given personally hand
by hand to every student and after explaining the objectives of the study to
the student, he/she was asked to pass the questionnaire to the parents to complete
it and not to leave any item empty. About four to sex questionnaires were distributed
per day. The distributed self-administered questionnaires were collected when
the students returned them back on the next day. For completing the Binet intelligence
test each student was interviewed separately in a quite suitable room. Nobody
was allowed to enter the room in order not to interrupt the student. Mild acute
illnesses were rolled out.
The team of work was consisted of the researcher and two will-trained psychologists
were needed to perform, evaluate and interpret the results.
The child was comfortably seated, greeting and candies were offered in order
to achieve a good relationship with him. Total testing time is 90-120 min, depending
on the students age and the number of subtests given. All test students
took an initial vocabulary test which along with the students age, determines
the number and level of subtests to be administered. Precise data about the
student was collected in short time. The basal level was assessed and used as
the entrance level in the following 14 items of the test.
Test scores provide an estimate of the level at which a child is functioning
based on a combination of many different subtests or measures of skills.
The numbers of correct responses on the given subtests are converted to Standard
Age Score (SAS) which is based on the chronological age of the test subject.
This score is similar to an I.Q. score. Based on these norms, the Area Scores
and Test Composite on the Stanford-Binet Intelligence Scale each have a mean
or average score of 100 and a standard deviation of 16. For this test, as with
most measures of intelligence, a score of 100 is in the normal or average range.
The standard deviation indicates how above or below the norm a child's score
is.Standard Age Score is then converted to Standard Age Score for areas through
special tables then composite overall score in other tables to obtain intelligence
Several methods were used for data collection: Self administrated questionnaire
sent to the students parents to detect gestational age, mode of delivery,
type of lactation, past medical and surgical history, socioeconomic status;
complete physical and medical examination; Cognitive functions were evaluated
by Stanford-Binet Intelligence Scales (SBS) Fourth Edition (Stanford-Binet IV)
and behaviour was assessed by child behaviour chick list.
Data management and analysis: All collected questionnaires were revised
for completeness and logical consistency. Pre-coded data was entered on the
computer using Microsoft Office Excel Software program for windows, 2003 after
being translated to English to facilitate data manipulation. Data was then transferred
to the Statistical Package of Social Science Software program, version 16 (SPSS)
to be statistically analysed. Description of quantitative variables in the form
of mean, Standard Deviation (SD), range, frequency and percentage were used.
Chi square and regression analysis tests were used for testing significance
of observed differences between studied groups. A multivariate linear regression
analysis was done to test for the significant predictors for knowledge score
among students. P values equal to or less than 0.05 were considered statistically
The study was conducted on a total number of 762 students including 72.9% children
delivered at full term and 27.1% children were delivered at preterm.
In the present study, male gender represent 66.7% of full term group, compared
to 65% of preterm group with no significant difference between both groups;
the most prevalent age group in full term group was 9-11 years, represents 39.9%
while in preterm group, the age group 7-9 years was the most common (55.3%)
with significant difference between both groups; the most common birth order
in full term group was the first (41.7%) and in preterm group (43.5%) with significant
difference between both groups; urban residence reported in 64% in group A compared
to 67% in group B with no significant difference; CS delivery was significantly
increased in group B (68.9% vs. 52.5%); the most common site of delivery was
hospital in both groups with significant increase in group B (83.5 vs. 71.0%,
respectively); NICU admission was significantly increased in group B (21.8%
vs. 5.0%); There was significant increase of NICU admission duration in group
B; there was significant decrease of breast feeding in group B (55.3% vs. 85.3%)
and the duration of feeding was significantly shorter in group B (Table
||Personal and obstetric characteristics of studied students
In the present study, there was significant increase of behaviour score (40-60
and >60) in group B (preterm) in comparison to full term group (26.2, 9.7
vs. 13.3, 4.7%, respectively). Similarly, there was significant increase of
enuresis and articulation disorders in preterm group (24.3 and 13.6%) vs. (13.7
and 4.3%) in full term group respectively). In addition, there was significant
decline of IQ in preterm in comparison to full term group (Table
Running regression analysis between total score IQ and other parameters revealed
that, there was significant correlation between IQ from one site and verbal
reasoning, abstract-visual reasoning, quantitative reasoning, short term memory,
aggression, attention problems, somatic problems from the other side in full
term group while in preterm group, this correlation was significant for verbal
reasoning, abstract-visual reasoning, quantitative reasoning, short term and
delinquency (Table 3).
||Comparison between studied groups as regard behavioural score,
In preterm cases, short term memory is highly correlated with IQ score so
it is the most affected items among studied children followed by Abstract-Visual
Reasoning and Delinquency more affected among preterm (Table 4).
DISCUSSION AND CONCLUSION
The present study represented a form of a cross sectional, nested, case control
study. For assessment of IQ, general cognitive and behavioral outcome at school
age in children born at term versus preterm in Damietta Governorate, Egypt.
Though this study gripped systematically the measuring of intelligence in children
at school age that provides a reliable assessment of general cognitive functioning;
It delineates that prematurity has an impact on intelligence total score, The
IQ scores, although within the normal range, were lower than full term that
is (108±14) in full term versus (104±16) in preterm.
Our study is in mean accordance with a random-effects meta-analysis that showed
the weighted significantly differences between the mean cognitive scores of
the preterm and the full term which was 10.9 in favour of the full term (Bhutta
et al., 2002). It also, agreed with the results of Begega
et al. (2010) who found that preterm children, in general, display
great heterogeneity in the impairment of the cognitive abilities assessed by
L-M form of the Stanford-Binet Intelligence Scale and showed that total preterm
score was (102±8.2) and full term (106±7.7). On the other hand
Walker et al. (2010) exhibited fewer cognitive
difficulties in preterm group than children in the control group. Compared with
normal birth weight NBW children, LBW-T children in the control group had poorer
selective attention and visual-spatial memory but there were no differences
in IQ, language, or behaviour. We could explain such difference by the methodological
tools applied and sample type.
The present study clarified that preterm birth and its complications affect
all domains of cognitive and language function. An alternative possibility is
that preterm birth is associated with domain-specific impairments that are dissociable
from general cognitive deficits but difficult to detect because they co-occur
with low IQ, Short term memory preterm score was (98.5±18.7) and full
term (104±8), followed by Verbal reasoning preterm score was (99.9±14.6)
and full term (102.4±11). Regression analysis between total score IQ
and the studied parameters in preterm, Short term memory is highly correlated
with IQ score so it is the most affected items among studied children followed
by Abstract-Visual Reasoning (fluid reasoning). These results go in alignment
with Taylor et al. (2000) and Luu
et al. (2011), who reported that, even after exclusion of preterm
subjects with significant disabilities, adolescents born preterm in the early
1990s were at increased risk of deficits in executive function and memory.
In addition it had been reported that, at neuropsychological assessment, preterm
children scored significantly lower than term comparison children in all tests.
After adjustment for cognitive level and maternal education, differences remained
statistically significant for verbal fluency (p<0.05), comprehension, short-term
memory and spatial abilities (Dall'oglio et al.,
Our results reveal that the preterm had more behaviour problems (35.9%) scoring
above the borderline cut-off (two folds the full term group). We found statistically
significance as regards behavioural score, about one forth preterm (26.2%) and
only 13.3% of full term showed positive behavioural score; about one tenth preterm
(9.7%) and only one fifth full term (4.7%) have dangerous behavioural score.
So, preterm were liable to abnormal or sever behavioural problems than full
term and Delinquency affection was significant among preterm with Regression
analysis for male Social problems and aggression are more prominent in females
depression and Delinquency are more prominent, so parents and paediatrician
should take care of Preterm children who exhibit higher rates of behaviour problems
early in development. Our results were in agreement with the meta-analysis of
Bhutta et al. (2002) who found that, Children
who were born preterm showed increases in externalizing or internalizing behaviours
in 13 (81%) of these 16 studies. Similarly, 9 (69%) of 13 studies found a significantly
higher prevalence of externalizing symptoms while 9 (75%) of 12 studies found
a significantly higher prevalence of internalizing symptoms in the cases vs.
Potharst et al. (2011) applied SDQ behavioural
score and found that normal full term (91.6%) versus preterm (61.5%), Mildly
abnormal (8.4), (38.5%) for full term and preterm, respectively, severely abnormal
(3.2), (18.3) for full term and preterm respectively Possible bright explanations
for this discrepancy may includethe difference in tools administered and geographic
Similarly, Van Baar et al. (2009) found that
the pretermchildren had more behavior problems (specifically internalizing problems
with 27% scoring above the borderline cut-off), as well as more attention-deficit/hyperactivity
disorder characteristics (specifically attention deficits).
Johnson et al. (2010) concluded that almost
one quarter of extremely preterm children had a psychiatric disorder at 11 years
of age. Behavioural score also correlates with total IQ score thus the lower
IQ was associated with abnormal or sever behavioural problem, so, there is considerable
difference between risk factors for different sex; the variables independently
associated with emotional symptoms are female gender, high parental stress and
poor general health. The factors associated with hyperactivity and inattention
is male gender, the variables associated with behavioural problems are living
in a non-traditional family, drug abuse in the family, higher parental stress
and harsh physical punishment.
Similarly Goodman et al. (2007) and Spittle
et al. (2009) found that Preterm children exhibit higher rates of
behaviour problems early in development, in particular internalizing and dysregulation
problems and poorer competence and lower IQ.
Other strength of the study is that its Comparison of intellectual quotient
level of studied groups regarding to behavioural problems and clarification
that one third preterm with enuresis and articulation disorders had lower IQ
scores, other problems as, encorpoesis, sleep disorders, nail pitting and sucking
had no significant difference.
Furthermore, Dai et al. (2007) concluded that
the total intelligence level of children with Primary Nocturnal Enuresis, (PNE)
was normal, but the M/C factor in the intelligence structure had some defects,
suggesting that PNE may be related to the abnormity of executive function in
the frontal lobe.
Barre et al. (2011) concluded that preterm
children have significantly poorer language function compared with control children.
These language difficulties are still present throughout primary school, a time
when language development becomes more stable and adult-like.
In addition, Dennis et al. (2009) found Prematurity
has a direct impact on verbal memory and linguistic processing speed which also
had classified as a fluid function and found that deficits in speech articulation
and prereading skills (<10th centile) were three to five times more frequent
in very preterm children. More than 18% of very preterm children had cognitive
deficits in more than five areas of functioning, compared with no control children.
The differences between very preterm children and controls remained highly significant
when only very preterm children and controls without major neuro-sensory impairment
Very preterm and/or VLBW children have moderate-to-severe deficits in academic
achievement, attention problems and internalizing behavioural problems and poor
EF which are adverse outcomes that were strongly correlated to their immaturity
at birth. During transition to young adulthood these children continue to lag
behind term-born peers (Aarnoudse-Moens et al.,
2009). In addition, the preterm child is at increased risk for sub-clinical
behavioural problems and can most often be described as inattentive, shy or
withdrawn and with poor social skills. Preterm children are more likely to have
psychiatric disorders, of which ADHD is the primary abnormal outcome. The lack
of co morbid hyperactivity and conduct disorders suggests a purer
form of attention deficit. There is also some evidence of increased risk for
Autistic Spectrum Disorders in VPT children but this requires further investigation
In short, results of the present study revealed that, preterm had lower total
score IQ so, preterm are vulnerable to cognitive affection. Preterm birth is
associated with domain-specific impairments and Short term memory is highly
correlated with IQ score so it is the most affected item among studied children.