By Karla Gale
Physical, mental, and social impairments affect the lives of many adults who were born prematurely, according to a national study in Norway, published in The New England Journal of Medicine.
"What most surprised us was the consistency of a dose-response relationship between gestational age and nearly all of the outcomes studied," lead author Dr. Dag Moster told Reuters Health. This means that the earlier the infant was born, the greater were the affects.
"On the other hand, we were reassured by our findings that the majority of preterm children without medical disabilities actually seemed to function very well as adults," Moster said.
The researchers, from University of Bergen, linked data from the national registries to identify children of different gestational age categories born between 1967 and 1983 and who survived until 2003. The study subjects included close to 870 000 infants of at least 23 weeks' gestational age without infants congenital anomalies.
Of the babies within the most preterm category, the risk of cerebral palsy increased over time, reflecting higher rates of survival among these vulnerable infants. Overall, six percent of those born between 28 and 30 weeks and nine percent of those born between 23 and 27 weeks had cerebral palsy, a statistically significant difference compared with full-term births.
"An ongoing study of children born in Norway in 1999-2000 demonstrates a survival rate to five years of age of 80 percent among 23-27 weekers, a notable increase compared to the 20 percent survival rate in our study. "Sadly, the rates of cerebral palsy in these two studies are very much the same," Moster commented.
The results also showed significant trends for mental retardation; disorders of psychological development, behaviour and emotion; and severe vision or hearing impairment or epilepsy.
When they excluded persons with medical disabilities from their analyses, there were small but statistically significant associations between gestational age and educational achievement, job-related income, finding a life partner, and of having children.
In contrast, there was no significant difference in unemployment rates, drug arrests, violent behaviour, or other criminal activity.
"There was an increased risk of disabilities even among moderate preterm children," whose numbers far exceed those of the most premature children, Moster pointed out. "Most research so far has focused on the most immature children, but the current study demonstrates that improving outcome for moderate preterm children would have an even greater impact on the number of disabled children."
"Studies are needed to identify modifiable factors that predict adult outcomes among children born prematurely in order to improve preventive and therapeutic strategies," the investigators conclude.