Medical advances have allowed doctors to save earlier and smaller babies. While some developmental problems are known to be common among such children, the long-term consequences were not entirely clear.
"We needed to have some idea of really what this group was like when they grew up," said one of the researchers, Dr. Neil Marlow, a neonatologist at the University of Nottingham in England.
Guidelines call for not resuscitating the most severely premature babies, but where to draw the line is a controversial and emotional decision. The study's findings might help guide doctors and parents about whether it is wise to use extreme measures.
"Parents need to go into this situation with their eyes wide open and with an open dialogue with their doctors as to what they should do," Marlow said.
Normal pregnancy is 37 to 42 weeks. Marlow and his colleagues looked at 241 children about 6 years old who had been born between 22 and 25 weeks. They found that 46 percent had severe or moderate disabilities such as cerebral palsy, vision or hearing loss and learning problems; 34 percent were mildly disabled; and 20 percent had no disabilities. Twelve percent had disabling cerebral palsy.
"This gives for the first time a real picture of what happens to these children who are at the limits of viability," said another researcher, Dieter Wolke of the University of Bristol in England. Their findings are reported in today's New England Journal of Medicine.
The rate of premature births in the United States has crept up in recent years, in part because of a rise in multiple births and older mothers.
"It's important to realize that prematurity is a major public health problem. One in eight babies are born prematurely," said Dr. Scott Berns of the March of Dimes.
In an accompanying editorial, Drs. Betty Vohr of Women and Infants Hospital in Providence, R.I., and Marilee Allen of Johns Hopkins Hospital in Baltimore, said the study shows the limits of what medicine can do to help such babies.
They cited publicity about "miracle babies" as one reason parents might seek to have their very premature child resuscitated. "We wish they all were little miracle babies, but they're not," Vohr said in an interview.