An American study on Monday said preterm babies born early in the third trimester of pregnancy may show poorer language skills in early childhood.

The brain imaging study shows that those preterm babies are likely to experience delays in the development of the auditory cortex, a brain region essential to hearing and understanding sound.

The new study reveals that such delays are associated with speech and language impairments at age 2.

The findings are reported in eNeuro, a journal of the Society for Neuroscience.

"We have a pretty limited understanding of how the auditory brain develops in preterm infants," said University of Illinois speech and hearing science professor Brian Monson, who led the study.

Monson and his colleagues turned to a large dataset collected at the St. Louis Children's Hospital Neonatal Intensive Care Unit between 2007 and 2010.

The 90 premature infants in the study had undergone magnetic resonance imaging one to four times in the course of their stay in the NICU. Another 15 full-term babies were recruited from the Barnes-Jewish Hospital in St. Louis and scanned within the first four days of life. The latter group is used for comparison with the preterm babies.

The team focused on the primary auditory cortex, which is the first cortical region to receive auditory signals from the ears via other parts of the brain, and the nonprimary auditory cortex, which plays a more sophisticated role in processing those stimuli.

The analysis revealed that by 26 weeks of gestation, the primary auditory cortex was in a much more advanced stage of development than the nonprimary auditory cortex.

Between 26 weeks and about 40 weeks -- the latter the equivalent of full-term birth -- the nonprimary auditory cortex in the preterm infants matured quickly, partially catching up to the primary auditory cortex.

Researchers found that both regions appeared less developed at 40 weeks in the preterm infants than in the full-term babies.

The team also found an association between the delayed development of the nonprimary auditory cortex in infancy and language delays in the children at age 2, suggesting that disruptions to this part of the brain as a result of premature birth may contribute to the speech and language problems often seen later in life in preemies, Monson said.

"It's exciting to me that we may be able to use this technique to help predict later language ability in infants who are born preterm," he said. "I hope one day we also will be able to intervene for those infants who may be at greatest risk of language deficits, perhaps even before they begin to use words."