Children with a birth weight under 2.5 kgs may be at increased risk of becoming underweight and can experience cognitive difficulties as well as diabetes and cardiovascular disease later in life, a study says.

The researchers found that early iron supplements seem to provide some protection. "The results were surprising. That low birth weight children who received early iron supplementation had a lower blood pressure in school age has never been shown before," said researcher Josefine Starnberg from Umea University in Sweden. "We may have identified a way to partially protect against cardiovascular diseases, even if more research is needed," Starnberg said in a statement released by the university.

The study involved 285 children who were born with a marginally low birth weight, 2 to 2.5 kg, and a control group of around 100 children born with a normal birth weight. Data on weight, height, body composition, blood pressure, and blood tests for blood sugar, insulin and blood lipids were collected. In addition, the children's IQ, and various other abilities were tested. The study showed that children born with only a little too low birth weight have more cognitive difficulties, such as lower verbal IQ and poorer attention and coordination abilities in comparison to children born with normal birth weight.

"The below average test results may lead to more school difficulties and behavioural problems to a larger extent than for children born with normal birth weight. It's important that we are aware of this, both in the health care system as well as in the educational system, in order to early capture those who may need additional support," Starnberg said.

Children born as marginally underweight have an increased risk of still being underweight at the age of seven, the findings showed.  Early signs of a disrupted insulin and blood sugar balance were also found, a well-known sign for increased risk of later developing diabetes and cardiovascular diseases. But infants who received iron supplementation in early childhood had lower blood pressure, which is a previously unknown relationship.