When mothers deliver later, babies are more likely to have physical problems, but they also are likely to have cognitive benefits down the road, suggests provocative new Northwestern University research to be published Monday in JAMA Pediatrics.
It is well known that continuing a pregnancy beyond 40 weeks can increase the risk of physical disabilities for the child, but this is the first study to document future cognitive benefits, as well as school-age physical risks, for late-term infants.
Full-term babies are delivered around 39 to 40 weeks. Late-term babies arrive around 41 weeks.
“Our hope is that this research will enrich conversations between OB-GYNs and expectant parents about the ideal time to have the baby,” said study lead author David Figlio, an economist and director of Northwestern’s Institute for Policy Research.
In the JAMA study, late-term infants, compared to full-term, had higher average test scores in elementary and middle school; a 2.8 percent higher probability of being gifted; and a 3.1 percent reduced probability of poor cognitive outcomes.
The late-term infants, however, also had a 2.1 percent higher rate of physical disabilities at school age and higher rates of abnormal conditions at birth.
“The tradeoff between cognitive and physical outcomes associated with late-term births is something parents and physicians should discuss,” said Figlio, also the Orrington Lunt Professor of Education and Social Policy at the Northwestern School of Education and Social Policy.
The researchers used a unique data set — matched birth and education records for more than 1.4 million Florida public school children — to find that late-term children did better in school in the long run but also had a higher risk of physical disability than their full-term counterparts.
“Armed with the information we learned from the work on birth weight and cognitive outcomes, we thought that longer gestation might be associated with improved cognition,” Figlio said. “We wanted to know: Is there more of a cost to delivering babies at full term than people previously thought?”