Children who have to be resuscitated at birth appear to be more likely to score poorly on IQ tests, even if they appeared healthy at first, report British researchers.

The findings, published on the website of The Lancet, come from Dr, David Odd of the Neonatal Intensive Care Unit at Southmead Hospital in Bristol, U.K.

The authors looked at children who had been resuscitated at birth but had no symptoms of neonatal encephalopathy, a term used to describe the signs of acute brain injury, such as seizures or altered responsiveness or tone.

They also looked at babies who had been resuscitated and had received neonatal care for symptoms of encephalopathy in their first month of life. They then compared the two groups to more than 10,000 children who had not needed to be resuscitated.

The researchers gave the children IQ tests when they were about eight years old. A low IQ score was determined to be less than 80.

The researchers found that the children who had developed symptoms of neonatal encephalopathy had more than a six-fold increased risk of a low IQ score compared with the children who had been born healthy.

But even children who had appeared healthy after birth but had been resuscitated had a 65 per cent increased risk for a low IQ score.

The estimated proportion of children with a low IQ score attributable to resuscitation at birth was 1.2 per cent of those who developed encephalopathy and 3.4 per cent for those who appeared healthy.

The authors note say that since most infants who require resuscitation don't show signs of encephalopathy, "they would have a larger population effect if a causal relation exists between resuscitation and the risk of a low IQ score."

The authors say the data suggest that even mild "cerebral events," such as being deprived of oxygen for even a short while during birth, might cause subtle defects in cognitive function that are only detectable as the child grows older.

Dr. Odd completed a similar study last year which found that low Apgar scores at birth are associated with an increased likelihood of low IQ scores at age 18.

An Apgar test evaluates a newborn's physical condition one minute and then again at five minutes after delivery.

However, that study found no association between a low first and second Apgar score and low functioning at school at age 15 and 16.

That study concluded: "Infants in poor condition at birth have an increased risk of poor functioning in cognitive tests at age 18, even if the infants recover quickly." However, his team added: "it is a relatively small effect and had little influence on educational achievement."