Babies Born Late Face Behavior Problems, ADHD
Credit: Yuri Arcurs | Dreamstime

Doctors have long known that preterm babies face increased health risks later in life, but now, new research from the Netherlands shows that post-term babies — those born after a 42-week pregnancy — also have a higher risk of developing behavioral and emotional problems, compared with children born at term.

The study showed that post-term babies were more than twice as likely to have behavioral problems at 18 to 36 months old compared with term babies. And post-term babies were almost 2.5 times as likely to have attention–deficit/hyperactivity disorder (ADHD) at these ages.

The results held even after the researchers controlled for a number of factors, including the mothers' weights, alcohol consumption and smoking frequency. However, the researchers said that other factors, including the mothers' nutrition during pregnancy, couldn't be ruled out as playing a role in the findings.

Doctors don't know what causes post-term births, but the researchers said it's imperative to solve this. "It is also important that further research is carried out in order to demonstrate a causal relation between post-term birth and behavioral problems," lead author Hanan El Marroun, a child psychiatrist at Erasmus MC, a medical center in Rotterdam, said in a statement.

Previous research has shown that both preterm and post-term births are linked with early health issues, and research has also shown that several long-term issues are associated with preterm births, such as a higher risk of cerebral palsy, sensory impairments and behavioral problems.

It's less clear whether there are similar long-term issues associated with post-term births, though a recent study, in which researchers tracked referrals to a neurologist or psychologist in Sweden, found that 13 percent of post-term children had a neurological or developmental disorder at age 5.

In the new study, researchers looked at pregnant women in Rotterdam who were due to give birth between April 2002 and January 2006. Of the 5,145 babies born, the researchers found that 4.4 percent were born preterm, and 7.4 percent were born post-term.

The mothers filled out a questionnaire, called the Child Behavior Checklist, when their toddlers were 18 months and 36 months old. Fathers also filled out the form at the 36-month mark.

The checklist asked questions about the child's behavior in the preceding two months, and is widely used to identify emotional problems, developmental problems and ADHD.

The researchers found that both preterm and post-term babies are at a higher risk for developing "problem behavior," compared with term-born infants.

The findings were limited in that the parents knew if their children were born post-term, and thus could have been biased to report more behavioral issues, the researchers noted. However, it's unlikely that they did this because "the notion that a post-term birth may signal at-risk babies is largely nonexistent in the medical profession, and absent in the public debate," the authors wrote in their study, published Wednesday (May 2) in the International Journal of Epidemiology.

Pass it on: Babies born more than two weeks after their due date may face an increased risk of behavior problems.