March 30 (HealthDay News) -- Even babies born near their due date have an increased risk of developmental delays when they reach kindergarten, new research shows.
Once thought to have little to no risk of long-term problems, healthy babies born between 34 and 36 weeks' gestation (considered "late pre-term") have as much as a 36 percent higher risk of a developmental delay or disability when they enter grade school, the study authors said.
"The risk to any individual baby born two to three weeks early is only about 4 percent, so we don't want parents to be alarmed," said study author Dr. Steven Morse, director of Community Newborn Services at the University of Florida. "But, we did want to get the attention of obstetricians who have a tough job balancing the medical risks to mother and fetus. This study adds a little bit more to the risk side."
Morse said the researchers also wanted pediatricians to be aware that there's an increased risk of developmental delays because they're the ones who care for the children as they grow.
The findings were published in the April issue of Pediatrics.
Most babies -- around 70 percent -- who are born early in the United States are born between 34 and 36 weeks of gestation. While the number of babies born at less than 34 weeks remained unchanged between 1990 and 2005, the number of babies born at 34 to 36 weeks rose by about 25 percent during the same period, according to the study.
"The majority of these are medically indicated births," said Morse.
Neonatalogist Dr. Jennifer Kloesz, of Children's Hospital of Pittsburgh, said that, while most deliveries between 34 and 36 weeks are done for medical reasons, "there may be some deliveries that probably can still be prolonged. We don't always aggressively try to stop labor at 34 or 35 weeks, and it could be that we need to start looking at that."
Morse and his colleagues evaluated Florida birth records between 1996 and 1997, and identified nearly 160,000 singleton infants born between 34 and 42 weeks to include in their analysis. Most of the children -- 152,661 -- were born between 37 and 42 weeks' gestation, which is considered full-term. Slightly more than 7,000 were born between 34 and 36 weeks. The researchers then compared birth information with pre-school and kindergarten school records.
They found that the risk of a developmental delay or disability was 36 percent higher for the babies born between 34 and 36 weeks. A developmental delay or disability may include physical, language, cognitive and socio-emotional development, according to the researchers.
The study also found that children who were born late pre-term had a 19 percent higher risk of being suspended in kindergarten. The risk of having to stay back in kindergarten was increased 11 percent for the children born early.
Morse said the researchers tried to control the data for the many factors that can influence a child's life between birth and school-age. They compensated for factors such as maternal age, education, socioeconomic states, maternal alcohol use and more.
He said the researchers think there's simply a lot of brain maturation that goes on during those last four weeks, and babies who are born early may be missing out on some of that growth process.
"This study shows that a late pre-term baby is not the same as a term baby," said Morse.
Kloesz added: "If you look at the risk for any one specific child, it's not terrible. But, if you look at all of these children, it's a huge societal risk."
SOURCES: Steven Morse, M.D., M.P.H., associate professor, pediatrics, and director, Community Newborn Services, University of Florida, Gainesville; Jennifer Kloesz, M.D., neonatologist, Children's Hospital of Pittsburgh; April 2009 Pediatrics