C-sections may raise autism risk – study

Delivery by Caesarean section is associated with an increased risk of autism in childhood, according to a study by Irish researchers.

Children born by Caesarean section have a 23 per cent greater risk of developing autism spectrum disorder (ASD), the study to be published shortly in the Journal of Child Psychology and Psychiatry suggests.

The researchers, led by Eileen Curran of University College Cork, also look at links between Caesareans and attention deficit and hyperactivity disorder (ADHD) but the findings were unclear.

The authors urge caution in interpreting their results and say more research is urgently needed to explore the risks involved. The study is a meta-analysis of 25 previously published papers on the links between Caesarean sections and conditions such as autism and ADHD. Some showed the risk of autism after a Caesarean increased by as much as 40 per cent.

The study says it is unclear what is driving this association and whether it is causal. Children born by Caesarean section have different gut flora than those born by normal delivery, and some scientists believe this may be a factor in psychological development.

Last weeks

Another theory derives from the fact Caesarean sections are normally carried out at 37-39 weeks, as opposed to a full 40-week gestation. “It is possible the last few weeks are important for brain development, and therefore being born near rather than at term may lead to an increased risk of psychological problems,” the study says.

However, the authors point out the underlying reasons for a Caesarean may lead to the increased risk of autism, not the Caesarean per se.

“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,” says Ms Curran.

Worldwide, an estimated 0.62 per cent of children are diagnosed with ASD, and 5.3 per cent with ADHD. The prevalence of autism has increased twentyfold since the 1980s, a rate that suggests factors other than improved detection and diagnosis.

The study cites worldwide Caesarean rates of over 20 per cent. Rates in Irish hospitals are increasing and range up to 38 per cent.