Combined, the two new, independent studies involved nearly 1,400 very low birthweight premature infants treated at 37 medical centers. The studies represent the largest clinical research effort of inhaled nitric oxide therapy in premature infants, and they offer promising advances in the care of very small premature babies, who are at high risk for delayed growth, lasting problems with their breathing and brain development, and other complications. Other studies of therapies to prevent these potentially debilitating long-term complications have yielded conflicting results. Supported by the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH), the studies' results are published in the July 27, 2006, issue of the New England Journal of Medicine in conjunction with a related editorial.

"Medical science has dramatically improved our ability to help very small and premature babies survive. But as the rate of premature births continues to rise, it is even more critical that we develop ways to prevent many of the complications related to prematurity so that these children can lead healthy, robust lives," NIH Director Elias A. Zerhouni, M.D., says.

In 2004, more than one-half million babies in the United States (about 12.5 percent) were born prematurely (less than 37 weeks of pregnancy) — the highest number reported since comparable national data have been available, according to the Centers for Disease Control and Prevention (CDC). Last year, costs associated with premature births in the United States totaled approximately $26.2 billion, or $51,600 per infant, according to a report released July 13 by an independent panel convened by the Institute of Medicine of the National Academies.

Breathing problems at birth are common among babies born very prematurely and at very low birthweight (under 3 pounds). Because their lungs are not fully developed, premature infants are likely to have trouble breathing continuously or on their own, a condition known as respiratory failure. Oxygen and, in many cases, use of a mechanical breathing machine, or ventilator, is used to help them breathe and to protect other organs such as the brain, heart, liver, and kidneys from damage while the lungs have a chance to mature.

However, high levels of extra oxygen or prolonged use of ventilators can damage the lungs and interrupt normal development, leading to a chronic lung disease known as bronchopulmonary dysplasia (BPD). Very small babies (those born weighing less than 1250 grams, or about 3 pounds) are at high risk for BPD even if they do not require a ventilator. BPD is associated with increased risk of ongoing lung problems such as pulmonary hypertension (high blood pressure in the arteries that supply blood to the lungs), sensitivities to secondhand smoke, asthma, and respiratory infections; neurodevelopmental problems such as cerebral palsy; learning disabilities; impaired growth; and cardiovascular problems. In the United States, more than 10,000 babies develop BPD each year.