According to a study carried out by Central South University in China, obese mothers were 47 per cent more likely to have children with the condition.
Researchers analysed the findings of multiple studies exploring the link between obesity during pregnancy and autism, using data from 200,000 people worldwide.
One theory is that high blood sugar levels in pregnant women could lead to higher than average levels in the child, which may affect the development of the brain and central nervous system.
The results have been published in the latest issue of the Journal of Autism and Developmental Disorders.
It is estimated that one in 100 children has autism in the UK. The condition affects how a person communicates with, and relates to, the people around them.
This is not the first time a link has been made between being overweight during pregnancy and autism.
In 2012, a study by the University of California found overweight mothers were 1.6 times more likely to give birth to a child with autism. The same mothers were also more than twice as likely to have a child with other developmental difficulties.
Carol Povey, director of the National Autistic Society's Centre for Autism, said, ‘This is an interesting and large analysis of past studies exploring potential links between maternal obesity and autism. However, aggregating studies with different designs can be problematic. And, as the authors recognise, further studies are needed before drawing conclusions. It’s particularly important not to suggest any causal link, when the study has only identified a possible association between obesity and autism.
‘The causes of autism are still unknown, though experts believe it does not result from a single cause and is rather a complex story of genes interacting with other genes, combined with environmental factors.
‘We therefore urge those thinking of starting a family not to jump to conclusions about these research findings or to allow them to affect the decisions they make.’