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Late-Term Births May Offer Future Cognitive Benefits

Children born at 41 weeks performed better in school than full term counterparts

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Babies born late have a higher probability of being gifted, and a lower probability of poor cognitive outcomes, but are more likely to be physically impaired.

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 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 cognitive benefits, as well as physical risks, for late-term infants.

David Figlio
David Figlio
Jonathan Guryan
Jonathan Guryan

“Our hope is that this research will enrich conversations between ob-gyns and expectant parents about the ideal time to have the baby,” said IPR director and education economist David Figlio, the lead author of the study. IPR economist Jonathan Guryan and IPR postdoctoral fellow Krzysztof Karbownik were also part of the team of researchers working on this study.

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. 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 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 setmatched birth and education records for more than 1.4 million Florida school childrento find that late-term (41 weeks) children did better in school in the long run, but also had a higher risk of physical disability than their full term counterparts (39 or 40 weeks).

The research builds on a previous study by Figlio’s team using the same Florida data set that found that heavier newborns have an academic edge.

“Armed with the information we learned from the work on birth weight and cognitive outcomes, we began thinking about the single best way to pack on more birth weight which means keeping the baby in utero longer,” Figlio said. “We wanted to know: Is there a cost associated with delivering these babies?” 

Figlio is Orrington Lunt Professor of Education and Social Policy and of Economics, and IPR Director. For more information, read the JAMA article, "Long-Term Cognitive and Health Outcomes of School-Aged Children Who Were Born Late-Term vs. Full-Term."

This article was originally published in Northwestern News.

Published: June 22, 2016.