Babies born a week early are more susceptible to develop learning difficulties and are at risk of serious problems such as autism or deafness.
More than 400,000 British children took place in the study, funded by the NHS, which showed that 8.4 per cent of the children who were born pre-term were found to have a learning difficulty, compared with just 4.7 per cent for those born at-term.
But study leader, Jill Pell, noted this rise but 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.
Nearly 18,000 of the children were classed as having Special Educational Needs such as dyslexia, or a physical difficulty such as deafness or poor vision.
The earlier the delivery, the greater the risk becomes: rising to 1.53 times for children born at 33 to 36 weeks, 2.66 times for those born between 28 and 32 weeks and 6.92 times for babies born between 24 and 27 weeks.
Almost one third of UK births take place at 37-39 weeks with more mothers choosing to have earlier deliveries for non-medical reasons.
