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The neurological development of very premature babies can be adversely affected by a number of factors surrounding the birth. A new study has found that exposure to stressors in the NICU can bring about changes in the structure and functions of the brain.

Early Exposure to Stress can Reduce the Brain Size and Effect its Proper Functioning

Although several studies done in the past have linked the neurological development of very premature babies to perinatal conditions, in a first study of its kind, the researchers have studied the effect of one such condition, namely the stress in the neonatal intensive care unit, on the development of the brain of the new born. They have found that early exposure to stress can reduce the brain size and effect its proper functioning.


The researchers selected 44 preterm babies, born before 30 weeks of gestation, for their study. All the babies were in the neonatal intensive care unit. The babies were examined to derive their Neonatal Infant Stressor Scale scores. This scale is based on the exposure of the babies to 36 stress producing events in the NICU including diaper changes, intravenous line insertion and intubation. The babies were also subjected to cerebral magnetic resonance imaging and different neurological tests to assess the development of their brains and cognitive functions.

The researchers found that exposure to stressors varies from baby to baby and also changes during the course of the hospital stay for a particular baby. However, the maximum stress is during the first 14 days following the delivery.

Preterm infants are at an Increased Risk of Developing Cerebral Palsy and Cognitive Impairments Apart from Increased Mortality

The researchers of the present study, led by Drs. Terrie Inder and Gillian Smith from St. Louis Children’s Hospital in Missouri, found that greater the exposure to different stress factors in the NICU, greater the chances of decreased frontal and parietal width. There were changes in the microstructure and neuronal connectivity in the temporal lobes of these very premature infants. The reflex scores were also lower in these babies. Neurobehavioral examination revealed abnormalities in the motor function. The research has been published in the October issue of the Annals of Neurology.


According to the latest statistics by the World Health Organization, 9.6 percent of all the births around the world are preterm, i.e. the baby is born before the 37th week of pregnancy. In the U.S, the incidence of preterm deliveries is 12 percent of all pregnancies, as per the data available with the National Institute of Child Health and Human Development.

These preterm infants are at an increased risk of developing cerebral palsy and cognitive impairments apart from increased mortality. The incidence of cerebral palsy in very premature babies born at 22 to 23 weeks of gestation is around 10 percent. Almost 40 percent of these babies may have mild motor deficiency while cognitive problems which include social and emotional issues may be present in up to 60 percent of very premature babies.

Most of these preterm babies are admitted to the NICU till the time they have matured enough to live without medical support. But in view of the findings of the recent study, further research is needed so as to expose these babies to minimal amount of stressors in the NICU.

  • • “Neonatal intensive care unit stress is associated with brain development in preterm infants”, by Gillian C. Smith, et al, Annals of Neurology, published in October 2011, accessed on November 10, 2011. Retrieved from http://onlinelibrary.wiley.com/doi/10.1002/ana.22545/abstract
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  • “Preterm infants exposed to stressors in NICU display reduced brain size”, public release on October 4, 2011, accessed on November 10, 2011. Retrieved from http://www.eurekalert.org/pub_releases/2011-10/w-pie092911.php
  • “Risks: Stress May Harm Preemies’ Development”, by Nicholas Bakalar, The New York Times, published on October 10, 2011, accessed on November 10, 2011. Retrieved from http://www.nytimes.com/2011/10/11/health/research/11risks.html
  • Photo courtesy of jdsmith1021 on Flickr: www.flickr.com/photos/jdsmith1021/4128423335