While it was already known that many premature babies face serious health challenges such as breathing, a new study has suggested that even relatively healthy preemies confront deficits in lung function that last into their second year, if not longer.
The new study, led by Marcus Herbert Jones, M.D., Ph.D., professor in the Department of Pediatrics at Pontificia Universidade Catolica do Rio Grande do Sul in Brazil, was published in the second issue for December of the American Journal of Respiratory and Critical care medicine.
"We have shown that healthy preterm infants have reduced lung function in the first months of life that persists into the second year of life. Healthy infants born prematurely may have smaller sized airways relative to the lung volume," Herbert said.
Those premature infants have less well developed lungs than their full term counterparts is well established, but researchers were not sure if preemies underwent a 'catch-up' period of lung function development.
To find out if that was the case, the research team recruited 26 preterm infants born between 30 and 34 weeks' gestation and compared their lung development and function to that of full term infants at about 10 weeks of age, then again at an average age of 15 months.
The team found that lung capacity and development relative to body size was similar between the groups, but airway function was consistently lower in the premature infants at both evaluations.
"We were unable to detect a catch-up period during the study. There was no change in the rate of increase of lung function when compared to full term infants," Dr. Jones said.
The team also found that premature infants who had more fully developed lungs, thus less need for supplemental oxygen after birth, actually faced greater respiratory problems than those who required prolonged supplemental oxygen.
"It is a counterintuitive finding. My interpretation is that in preterm infants, supplemental oxygen may be a marker of a less mature lung, which may have a better long term respiratory prognosis than infants with accelerated maturation due to prenatal events such as infection and inflammation," Dr. Jones said.
Maternal tobacco smoking was also associated with lower lung function in both premature and full term infants in both evaluations, suggesting a long lasting effect of smoke exposure on infant lung growth and development.
The finding supports a number of other studies that have similarly found that maternal smoking adversely affects lung function in both full term and preterm infants.
While researchers postulate that the preterm infants' reduced lung function may be due to airways that do not develop at the same rate as their lung volume, they also highlight other possible explanations, including more compliant airways, increased bronchial tone, or decreased pulmonary elastic recoil, and advocate further research to determine why preterm infants face persistent deficits in lung function.
"These subjects have decreased airway function not only in the first few months of life, but also at the one year follow-up evaluation. The persistence of reduced expiratory flows in healthy preterm infants may contribute to their increased risk of respiratory illnesses early in life," Dr. Jones said.