By Kate Kelland
LONDON (Reuters) Jun 09 - Babies born just 1 or 2 weeks before their 40-week gestation due date are more likely to develop learning difficulties such as autism or dyslexia, according to a British study published on Tuesday.
The findings show that even babies born at 39 weeks have an increased risk of a developing a learning disability compared with babies born a week later.
Scientists in Scotland, analyzing the birth history of more than 400,000 schoolchildren, found that while babies born at 40 weeks have a 4% risk of learning difficulties, those born at 37 to 39 weeks of gestation have a 5.1% risk.
"There was an increasing risk of special educational needs as the gestation date fell, so as deliveries got earlier, the risk went up," said Jill Pell, an expert in public health and health policy Glasgow University, who led the study.
"Even being just a week early put the risk up."
It is already known that a baby born prematurely is more likely to have learning difficulties. But the risks for babies born in the 24 to 40 week range had not previously been studied.
Pell found that although the risk of educational difficulties was much higher in preterm than in early term babies, the absolute numbers of children with difficulties in the 37 to 39 week group were higher, because many more babies are born at this time than before 37 weeks.
In her study, early term births accounted for 5.5% percent of cases of learning disabilities, while preterm deliveries accounted for only 3.6% of cases.
According to the World Health Organization, more and more women worldwide are delivering by cesarean section and a "significant proportion" of these surgical procedures are performed without any clear medical need.
Rates of autism have also been rising, but Pell said it would be "a leap too far" to link her findings directly to rates of autism, since autism was only one of a range of learning difficulties considered.
Pell, whose study was published online June 8th in Public Library of Science (PLoS) Medicine, acknowledged that cesarean sections were not the only factor behind early-term births. But she said doctors and women should include the risks of learning difficulties when considering a cesarean.
"It is now normal policy (in cesarean section) to deliver women a week early," she said in a telephone interview. "But if you make a decision...for an elective pre-term delivery, then it has to be a balance, weighing up the risks and potential benefits.
"What this study shows is that special education needs are another factor that need to be considered."
PLoS Medicine 2010.