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 “There has been quite a lot of research on very preterm birth and
the increased risk for ADHD but less evidence when it comes to late
preterm birth (weeks 34-36) and even less regarding babies born
early term (weeks 37-38),” said lead author Dr. Minna Sucksdorff of
the University of Turku in Finland.
In premature babies, the brain is still developing, and whatever
caused the preterm birth, like an infection in the mother, may have
affected the brain, Sucksdorff told Reuters Health by email.
Researchers used three Finnish health registries to identify 10,321
children diagnosed with ADHD who had been born between 1991 and
2005. They compared each child with ADHD to four children without
ADHD who had a similar birth date, gender and place of birth.
The registries included data on gestational age at birth, which was
calculated using the mother’s last menstrual period and first
trimester ultrasound. Forty weeks is considered “full term.”
Based on standards for each week of gestational age, the researchers
noted which babies had been born of average weight, smaller than
average or larger than average.
Mother’s age, substance abuse and smoking during pregnancy, number
of previous births, marital status, father’s age, and the urbanity
of the child’s birthplace were associated with gestational age,
birth weight and ADHD, the authors reported in Pediatrics.
Accounting for other factors, premature birth was still associated
with ADHD, with the risk increasing steadily as gestational age
decreased.
Babies born at 25 weeks of gestational age were more than five
times, or 500 percent, more likely to be diagnosed with ADHD as
those born at 40 weeks.
At 38 weeks, babies were about 12 percent more likely to develop
ADHD than those born full term.
Infants born significantly small or large for their gestational age
also had an increased risk of ADHD.
This is not surprising, said Guilherme Polanczyk of the University
of Sao Paulo Medical School in Brazil, as there is good evidence
showing that prematurity and poor fetal growth are associated with a
variety of chronic disorders such as high blood pressure,
cardiovascular disease, diabetes, and mental disorders, including
ADHD.
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The fact that even some early term babies, who would not be
considered premature, had an increased risk may indicate that the
risk is continuous, with no specific cut-off point, he said by
email.
“It is very interesting that those big for gestational age also have
an increased risk,” he said. “This is consistent with a large body
of evidence showing that deviations of brain development may also
occur in this population, probably because of different disease
mechanisms.”
Polanczyk was not part of the Finnish study.
“It is more and more established that prenatal health is very
important also for mental, emotional, and cognitive development,”
Polanczyk added. “Preventing preterm birth is always an important
goal, because it has a causal role to a variety of other negative
outcomes.”
Identifying children with increased ADHD risk may improve early
detection and intervention, which can help reduce the adverse
outcomes of ADHD, he said.
According to Sucksdorff, about five percent of children worldwide
are diagnosed with ADHD.
SOURCE: http://bit.ly/1NPjxue Pediatrics, online August 24, 2015.
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