A paper published in the latest issue of the International Journal of Epidemiology suggests that infants born after the normal human gestational period (42 weeks) are more likely to develop emotional and behavioral problems later on in life.
These problems begin to manifest themselves since early childhood. In this subgroup of the general population, the incidence of conditions including attention deficit hyperactivity disorder (ADHD) is very high, say researchers from the Netherlands.
The work was led by Hanan El Marroun, PhD, a postdoctorate fellow in the Department of Child and Adolescent Psychiatry at Sophia Children's Hospital and Erasmus Medical Center, in Rotterdam.
The new investigation revealed a U-shaped curve in the association between infants' time of birth and their risks of developing emotional and behavioral problems during childhood. This suggests that both pre- and post-term babies are subjected to the same, elevated risks, PsychCentral
“Post-term children have a considerably higher risk of clinically relevant problem behavior and are more than twice as likely as term-born children to have clinical ADHD,” says El Marroun, who was also the lead author of the new paper detailing the findings.
The research was carried out on a number of 5,145 babies, born in Rotterdam between April 2002 and January 2006. The large, population-based survey was dubbed the Generation R Study. Mothers who were expecting during this period were asked by their midwives and gynecologists to participate.
Out of this baby sample, about 7 percent (382 infants) were born after the normal gestation period, while about 4 percent (226 babies) were born ahead of term. Questionnaires were then sent to the parents when their children were 18 and 36 months old.
The abnormal emotional and behavioral development may be caused by a lack of nutrients, and diminished oxygen flow, through the placenta. If a baby goes past its delivery term, then its growth requires resources that the placenta simply cannot provide in sufficient amounts.
This lack of nutrients and oxygen can lead to abnormal fetal development, which may in turn cause the problems scientists have uncovered.