Babies weighing as little as 1-1/2 pounds would not have survived a generation ago, but through recent technological advances, most of these children are able to live today. However, some of that life-giving technology is also exacting a price on the kids, according to a new study published in the December issue of the medical journal Pediatrics.
Investigators from Case Western Reserve University's School of Medicine found that a significant percentage of very low birth weight babies sustain long-term cognitive and motor developmental problems if they suffer from the lung disease called bronchopulmonary dysplasia (BPD).
Very small premature infants have a high chance of having BPD because it is caused by prolonged exposure to mechanical ventilation, which premies need because of underdeveloped lungs. BPD is now the leading cause of lung disease in U.S. infants and the third leading cause of chronic lung disease in children.
The study found that by 3 years of age, about 21 percent of infants with BPD tested in the range of retardation, compared to less than 10 percent of very low birth weight babies without BPD, and less than 3 percent of term babies.
"We found that independent of any other complications of prematurity, kids at 3 years of age who had BPD as infants who had been premature had some motor problems that were associated with BPD, " said Lynn Singer, the study's lead author and a professor of pediatrics. "Motor problems included things like balance, holding crayons and pencils, and eye-hand coordination."
On the other hand, said Singer, "In terms of their language and mental development, BPD was not related to any additional problems for them at 3 years of age. However, because BPD babies were smaller and sicker, they had higher rates of delay at 3 years."
Singer said that BPD may be a factor in the higher rates of learning disabilities that pre-term babies experience at school age.
The study examined three groups of 329 infants in the neonatal intensive care units at three Cleveland hospitals; 122 had very low birth weight and had BPD, 84 had very low birth weight without BPD, and 123 were full-term.
Very low birth weight babies are under three pounds and are born as young as 24-25 weeks. (The normal duration of pregnancy is about 40 weeks.)
The investigators used standard tests for mental and motor development, and controlled for medical and social factors that could also affect the children's outcomes.
Singer said that the phenomenon of these very young infants surviving is a recent development for which health professionals lack data on long-term development.
"As a result, it was very hard to tell families what the prognosis would be long-term, " Singer said. "But I want to emphasize that 80 percent of these children are functioning within normal ranges. Considering that a few years ago these kids would not have survived, this is quite an accomplishment."
The study was funded by the Maternal Child and Health Bureau (part of the U.S. Health and Human Services Department) and the Heart Lung and Blood Institute of the National Institutes of Health.
Singer recently received funding from the Maternal and Child Health Bureau to look again at these children, who were born in 1989 and are now 8 years old. "We know from the research literature on premies in general that these kids at school age have more learning disabilities. We want to find out whether these motor problems persisted when they went to school, whether they resolved, and whether or not they might be related to higher incidence of learning disabilities that you see in groups of premie babies when they're at school age, " said Singer.
Other researchers on the study include Toyoko Yamashita, Lawrence Lilien, Marc Collin, and Jill Baley. The hospitals involved were University Hospitals of Cleveland, MetroHealth Medical Center, and Fairview General Hospital.
Journal
PEDIATRICS