Premature babies are three times more likely to be hospitalised with infections later in childhood, a major Oxford study has found.
Health risks associated with being born earlier than 37 weeks (more than three weeks before the normal gestational period of 40 weeks) decline as children get older.
However, hospital admissions among seven to 10 year-olds were three times higher for those born very early, before 28 weeks, according to researchers at the University of Oxford.
The number of premature babies admitted to hospital was also six times higher than those born at 40 weeks, the study revealed.
Infections, as well as respiratory and gastrointestinal conditions, are responsible for many hospital admissions.
Data on more than a million children born in NHS hospitals between Jan 1, 2005 and Dec 31, 2006 was analysed by the researchers.
Prof Maria Quigley, who led the study, said: "Our findings indicate that gestational age at birth is a strong predictor of childhood illness, with those born extremely preterm being at the greatest risk of hospital admission throughout childhood.
"And the finding that infections were the main cause of excess hospital admissions at all ages prompt us to call for targeted strategies to help prevent and better manage childhood infections."
Around 60,000 babies are born prematurely in the UK every year.