Children born prematurely often suffer from long-term health complications, but a new Dutch study suggests late babies can also be saddled with some of the same troubles.
The researchers found "post-term" infants – those born after a pregnancy of 42 weeks – are at heightened risk of developing behavioural and emotional problems, especially attention deficit hyperactivity disorder.
"At the time these children were born, we did not have a clue that post-term births could be related to any behavioural problems," said the lead scientist, Hanan El Marroun, at Erasmus Medical Center and Sophia Children's Hospital in Rotterdam.
For the study, the researchers recruited pregnant women who were willing to have their children assessed on a regular basis. In total, the study included 5,145 babies born between April, 2002, and January, 2006. Out of that group, 226 (or about 4 per cent) were born preterm, and 382 (or about 7 per cent ) were post-term. Some of the late babies were in the womb for up to 10 months.
During the follow-up at 18 and 36 months, the parents were asked to complete questionnaires about their child's development.
Those answers revealed that both premature and late-term babies had more behavioural and emotional problems than kids born full term. In particular, preterm infants were 2.3 times more likely to show clinical signs of ADHD, compared to full-term children. Similarly, late-term children were twice as likely to display evidence of ADHD than full-term kids.
"In the Netherlands, we have a belief that childbirth should come naturally. And the midwives always say the baby knows best when to enter the world," said Dr. Marroun.
In Canada, doctors are much more likely to intervene at an earlier stage of a prolonged pregnancy. In fact, Canadian physicians are sometimes accused of being too quick to induce labour or using cesarean section for delivery.
A pregnancy is considered normal until 41 weeks, according to the Society of Obstetricians and Gynecologists of Canada. Based on SOGC guidelines, a physician will offer measures to induce labour at 41 weeks and then advise for induction at 42 weeks.
In their study, published in the International Journal of Epidemiology, the Dutch researchers suggest several theories that may account for the apparent long-term complications. For instance, the placenta – the organ that connects the developing fetus to the uterine wall – may start to deteriorate as the pregnancy goes past the normal due date. That could mean the infant lacks adequate levels of oxygen and nutrients during the final days in the womb.
"But, to be honest, we don't really know why this may be happening," said Dr. Marroun. "So it is really important to dive into this topic and try to figure it out."
More research will be needed to confirm the Dutch findings, but Dr. Marroun hopes her study will raise awareness about potential long-term problems.