Academics warn the increasingly popular Caesarean section deliveries heighten the risk of developing autism by 23 per cent.

Babies born through Caesarean section are more likely to develop autism, a new study says.

Academics warn the increasingly popular C-section deliveries heighten the risk of the disorder by 23 per cent.

However, they urge caution on the findings and have stressed more research is needed.

Professor Louise Kenny, one of the authors and a practising obstetrician, said the link between C-sections and children developing Autism Spectrum Disorder also remains unclear.

"Parents should be reassured that the overall risk of a child developing ASD is very small and that Caesarean section is largely a very safe procedure and when medically indicated, it can be lifesaving," she said.

The study was carried out by University College Cork and was been published in the Journal of Child Psychology and Psychiatry on Monday.

It reviewed existing findings from studies on C-section and ASD in a number of countries including Australia, the United States, Canada and Sweden.

They also looked for any links between the surgical delivery of a baby and attention deficit and hyperactivity disorder.

But there were only two studies to review and their findings were unclear.

Eileen Curran, lead author of the report, said the relationship between the type of delivery used in childbirth and psychological development is complex.

"Given the accelerating rate of Caesarean section globally, this finding warrants further research of a more robust quality using larger populations to adjust for important potential confounders and explore potential causal mechanisms," she said.

The rate of births by C-section has been rising steadily in recent years.

The World Health Organisation recommends that no more than between 10 per cent and 15 per cent of births should be through the surgical method.

Last year, a study published in the British Medical Journal said the number of new cases of autism being diagnosed had levelled off after a surge in reported cases during the 1990s.

It suggested increased awareness and diagnosis of the condition were behind the earlier rising rates.

However a report by the US Centre for Disease Control claimed a 78 per cent rise in autism cases between 2002 and 2008.

Autism is a lifelong neuro-developmental disability leading to difficulties in communicating and forming relationships with people.

Those with the disorder can also have problems with language and making sense of the world around them.

Copyright AAP 2014.