Babies born before 39 weeks are more likely to have symptoms associated with attention deficit hyperactivity disorder (ADHD), according to a study published in the Journal of Pediatrics.
ADHD is estimated to affect more than 6 percent of school-age children. The disorder appears in childhood with symptoms of hyperactivity, impulsiveness and lack of attention. It has already been shown to be linked to premature births (less than 37 weeks gestation).
This study is one of the few that focuses on babies born between 37 and 41 weeks and relates gestational age to the diagnosis or symptoms of ADHD. Data from about 1,400 children were analysed and it was found that children born between 37 and 38 weeks had significantly higher ADHD symptom scores than children born between 39 and 41 weeks. Specifically, the researchers found that each week of gestational age was associated with 6% lower hyperactivity scores and 5% fewer ADHD symptoms and cognitive problems.
It is also the first study to include reports from teachers, which, together with parents' reports and doctors' evaluations, provide very valuable information for the diagnosis of ADHD. Symptoms reported by the mother generally reflect behaviour at home or in small family groups. However, symptoms reported by teachers reflect behaviour in an educational environment with a large number of children.
The explanation behind this finding is linked to the brain development that occurs during these weeks of pregnancy. Significant growth occurs in different types of brain cells between 34 and 40 weeks of gestation. Babies born late probably benefit from one to two extra weeks of intrauterine brain development, compared to those born before 40 weeks.
These data add to the evidence that supports recommendations to delay elective deliveries to at least 39 weeks. They also suggest that it may be advisable to screen babies born between 37 and 38 weeks for ADHD symptoms.
