Washington: Infants born prematurely are placed in the neonatal intensive care unit (NICU) to help them develop fully. They are likely to be exposed to stress factors at the unit which could decrease their brain size and functional connectivity.

Some of these stress factors are low body temperature, infections, variations in blood sugar levels, insufficient oxygen reaching their underdeveloped tissue and brains.

Infants born before the 37th week of pregnancy are considered preterm, which occurs in 9.6 percent of all births worldwide, according to the Bulletin of the World Health Organisation (WHO), the journal Annals of Neurology reports.

A study, led by Terrie Inder and Gillian Smith, both Washington University researchers at St. Louis Children's Hospital, Missouri, is the first to report on the effects of stress among hospitalised preterm infants and its impact on brain development.

For their observational study, the research team recruited 44 preterm infants within 24 hours of birth from November 2008 to December 2009, according to a St. Louis statement.

Results show that the average daily exposure to stressors was greatest in the first 14 days following birth. “Our findings suggest that stress exposure reduces the brain size in early preterm infants and long-term consequences are unknown,” said Inder.

Besides increased mortality risk, prior studies have shown that up to 10 percent of every preterm infants (22-32 weeks gestation) have cerebral palsy, nearly 40 percent display mild motor deficiency, and up to 60 percent experience cognitive impairments.