WEDNESDAY, May 16 (HealthDay News) -- Full-term babies with a low birth weight (5.5 pounds) have a significantly increased risk of developing respiratory symptoms such as coughing, wheezing and pulmonary infections up to age five, and that risk is even greater if these children are exposed to secondhand smoke, says a Dutch study.

The association between birth weight and respiratory symptoms decreased after age five and was not significant by age seven.

Researchers analyzed data on more than 3,600 full-term, low-birth-weight babies. They found that during the first seven years of life, almost 39 percent of them had at least one wheezing episode, close to 52 percent had cough at night, and more than 37 percent had a lower respiratory infection.

"Overall, 70 percent of the cohort had reported at least one respiratory symptom at some point in the first seven years of life," Dr. Johan C. de Jongste, a professor in the department of pediatric respiratory medicine at Erasmus MC/Sophia Children's Hospital, said in a prepared statement.

"Size and maturity are major factors in the development of the lung. In children with diminished prenatal growth, and consequently low birth weight, a disturbed lung development is associated with a relatively small airway caliber. This can cause decreased lung function and more respiratory symptoms later in life," de Jongste said.

He and his colleagues also found that a full-term, low-birth-weight child had an additional 6 percent increased risk of respiratory symptoms if the child was exposed to secondhand smoke after birth.

The study is published in the second issue for May of the American Journal of Respiratory and Critical Care Medicine.

More information

The American Association for Respiratory Care has more about children and lung health.

-- Robert Preidt

SOURCE: American Thoracic Society, news release, May 15, 2007

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